A self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions and its preparation method

Abstract

This invention discloses a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions, and its preparation method, belonging to the field of polymer composite materials. The method includes: Step 1, preparing isocyanate dimer-modified boron nitride nanosheets and polyphenolamine-modified graphene nanosheets respectively; Step 2, dispersing the first type of nanosheets in a polyurethane prepolymer solution for in-situ polymerization, casting to form a film, obtaining a composite film of isocyanate dimer-modified boron nitride nanosheets and polyurethane prepolymer; dispersing the second type of nanosheets in a polyurethane prepolymer solution for in-situ polymerization, casting to form a film, obtaining a composite film of polyphenolamine-modified graphene nanosheets and polyurethane prepolymer; Step 3, using the first composite film obtained in Step 2 as an intermediate insulating layer, and the second composite film as upper and lower electromagnetic shielding layers, stacking them into a sandwich structure and then hot-pressing to obtain the self-healing polyurethane insulating composite material. The material prepared by this method has both thermal conductivity and electromagnetic shielding functions.

Description

Technical Field

[0001] This invention relates to the field of polymer composite material preparation technology, and in particular to a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions, and its preparation method. Background Technology

[0002] With the iterative updates of wireless communication and microelectronics technologies, electronic components are gradually developing towards integration, miniaturization, and functionalization. While this trend improves the performance of electronic components, it also significantly increases their power density per unit volume, leading to continuous heat accumulation during operation and generating severe electromagnetic interference. Excessive heat accumulation reduces the stability and reliability of equipment operation and shortens its lifespan; while electromagnetic interference not only affects the normal operation of nearby electronic systems but also has adverse effects on human health. Therefore, developing polymer-based thermal interface materials with electromagnetic shielding functions has become crucial for the safe and stable operation of electronic components. Currently, the main method for preparing polymer-based thermal interface materials with electromagnetic shielding functions is to fill the polymer matrix with conductive fillers. When the conductive fillers form conductive channels, the thermal conductivity and electromagnetic shielding efficiency of the composite material are greatly improved. However, highly conductive thermal interface materials are prone to causing internal short circuits in electronic components, and thermal interface materials are susceptible to mechanical damage during long-term use, leading to a sharp decline in their performance. Therefore, how to provide self-healing polymer-based composite materials that combine high thermal conductivity and electromagnetic shielding performance while maintaining good insulation properties is a problem that needs to be solved.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions, and a method for preparing the same. The prepared self-healing polyurethane composite material has excellent thermal conductivity and electromagnetic shielding functions, while maintaining good insulation properties, thus meeting the needs of modern electronic devices for high-performance thermal interface materials and solving the aforementioned technical problems in the prior art.

[0005] The objective of this invention is achieved through the following technical solution: A method for preparing a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions, comprising: Step 1: Prepare two types of nanosheets respectively: Boron nitride nanosheets modified with isocyanate dimers were prepared. Polyphenol amine-modified graphene nanosheets were prepared using polyphenol amine-modified graphene nanosheets. Step 2: First, prepare the polyurethane prepolymer, then prepare two composite films separately: The isocyanate dimer modified boron nitride nanosheets obtained in step 1 are dispersed into the prepared polyurethane prepolymer for in-situ polymerization, and then cast into a film to obtain a composite film of isocyanate dimer modified boron nitride nanosheets and polyurethane prepolymer. The polyphenol amine modified graphene nanosheets obtained in step 1 are dispersed into the prepared polyurethane prepolymer for in-situ polymerization, and then cast into a film to obtain a composite film of polyphenol amine modified graphene nanosheets and polyurethane prepolymer. Step 3: The isocyanate dimer-modified boron nitride nanosheets and polyurethane prepolymer composite film prepared in Step 2 are used as the intermediate insulating layer. The polyphenol amine-modified graphene nanosheets and polyurethane prepolymer composite film are placed on the upper and lower layers of the intermediate insulating layer, respectively, as the upper electromagnetic shielding layer and the lower electromagnetic shielding layer. After stacking to form a sandwich structure, they are hot-pressed to obtain a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions.

[0006] A self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions, prepared by the method described in this invention, is made by using isocyanate dimer modified boron nitride nanosheets and polyurethane prepolymer composite film as the intermediate insulating layer, and placing polyphenol amine modified graphene nanosheets and polyurethane prepolymer composite film on the upper and lower layers of the intermediate insulating layer respectively as the upper and lower electromagnetic shielding layers. The self-healing polyurethane composite material is obtained by hot pressing after stacking to form a sandwich structure material.

[0007] Compared with existing technologies, the self-healing polyurethane composite material and its preparation method that combine thermal conductivity and electromagnetic shielding functions provided by this invention have the following advantages: A novel self-healing polyurethane composite material was prepared by means of molecular structure design, filler-matrix interface optimization, and composite material structure control. This composite material has excellent thermal conductivity and electromagnetic shielding properties, while maintaining good insulation and self-healing properties. It can well meet the requirements of modern electronic devices for high-performance thermal interface materials. Moreover, the preparation process is simple, the reaction conditions are mild, and the product quality is stable. This composite material can well meet the needs of electronic devices and has great application potential in the fields of electronic devices. Detailed Implementation

[0008] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments, and do not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0009] First, the following explanations are provided for the terms that may be used in this article: The term "and / or" means that either or both can be achieved simultaneously. For example, X and / or Y means that it includes both "X" or "Y" as well as the three cases of "X and Y".

[0010] The terms "comprising," "including," "containing," "having," or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example, including a technical feature element (such as raw material, component, ingredient, carrier, dosage form, material, size, part, component, mechanism, device, step, process, method, reaction conditions, processing conditions, parameter, algorithm, signal, data, product or article of manufacture, etc.) should be interpreted as including not only the expressly listed technical feature element, but also other technical feature elements that are not expressly listed and are well-known in the art.

[0011] The term "composed of" excludes any technical features not expressly listed. When used in a claim, it closes the claim to exclude all technical features other than those expressly listed, except for associated conventional impurities. If the term appears only in a clause of a claim, it limits the claim to the elements expressly listed in that clause; elements recited in other clauses are not excluded from the overall claim.

[0012] The term "parts by mass" indicates the mass ratio between multiple components. For example, if component X is described as x parts by mass and component Y as y parts by mass, then the mass ratio of component X to component Y is x:y. One part by mass can represent any mass; for example, one part by mass can be expressed as 1 kg or 3.1415926 kg, etc. The sum of the parts by mass of all components is not necessarily 100 parts; it can be greater than 100 parts, less than 100 parts, or equal to 100 parts. Unless otherwise stated, parts, proportions, and percentages mentioned herein are all measured by mass.

[0013] When concentration, temperature, pressure, size, or other parameters are expressed as numerical ranges, such ranges should be understood to specifically disclose all ranges formed by any pairing of upper limits, lower limits, or preferred values ​​within that range, regardless of whether the range is explicitly stated; for example, if the numerical range "2 to 8" is stated, then that range should be interpreted to include ranges such as "2 to 7", "2 to 6", "5 to 7", "3 to 4 and 6 to 7", "3 to 5 and 7", "2 and 5 to 7", etc. Unless otherwise stated, the numerical ranges described herein include both their endpoints and all integers and fractions within that range.

[0014] The technical solution provided by this invention will be described in detail below. Contents not described in detail in the embodiments of this invention are prior art known to those skilled in the art. Where specific conditions are not specified in the embodiments of this invention, they shall be performed according to conventional conditions in the art or conditions recommended by the manufacturer. Reagents or instruments used in the embodiments of this invention whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0015] This invention provides a method for preparing a self-healing polyurethane composite material that combines thermal conductivity and electromagnetic shielding functions, comprising the following steps: Step 1: Prepare two types of nanosheets respectively: Boron nitride nanosheets modified with isocyanate dimers were prepared and can be denoted as BNNS@DI. Polyphenol amine-modified graphene nanosheets were prepared using polyphenol amine-modified graphene nanosheets, which can be denoted as GNP@PPA; Step 2: First, prepare the polyurethane prepolymer, and then prepare two types of composite films: The isocyanate dimer modified boron nitride nanosheets obtained in step 1 are dispersed into the pre-prepared polyurethane prepolymer for in-situ polymerization, and then cast into a film to obtain a composite film of isocyanate dimer modified boron nitride nanosheets and polyurethane prepolymer, which can be denoted as BNNS@DI-PU. The polyphenol amine modified graphene nanosheets obtained in step 1 are dispersed into the pre-prepared polyurethane prepolymer for in-situ polymerization, and then cast into a film to obtain a composite film of polyphenol amine modified graphene nanosheets and polyurethane prepolymer, which can be denoted as GNP@PPA-PU. Step 3: The isocyanate dimer modified boron nitride nanosheets and polyurethane prepolymer composite film (i.e., BNNS@DI-PU) prepared in Step 2 are used as the intermediate insulating layer. The polyphenol amine modified graphene nanosheets and polyurethane prepolymer composite film (i.e., GNP@PPA-PU) prepared in Step 2 are placed on the upper and lower layers of the intermediate insulating layer, respectively, as the upper electromagnetic shielding layer and the lower electromagnetic shielding layer. After stacking to form a sandwich structure, they are hot-pressed to obtain a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions, which can be referred to as SWPU.

[0016] Preferably, in step 1 of the above method, isocyanate dimer-modified boron nitride nanosheets (BNNS) are prepared by modifying boron nitride nanosheets with isocyanate dimer DI in the following manner: Prepare a hexagonal boron nitride (BN) dispersion of 6–33 g / L, ball mill it at 200–800 r / min for 4–12 h, then centrifuge and vacuum dry it to form exfoliated hexagonal boron nitride nanosheets (i.e., BNNS). Prepare a dispersion of exfoliated hexagonal boron nitride nanosheets at a concentration of 6–33 g / L. Add 0.1–1 g / L isocyanate dimer (DI) and 0.1–0.3 wt% catalyst to the dispersion. Set the stirring speed to 600–1000 r / min and magnetically stir at a constant temperature of 20–80 °C for 2–4 h. Filter and dry the mixture to obtain isocyanate dimer-modified hexagonal boron nitride nanosheets, which can be denoted as BNNS@DI.

[0017] Preferably, in the preparation of isocyanate dimer modified boron nitride nanosheets in step 1 above, the average size of the unmodified hexagonal boron nitride (BN) is 1–60 μm and the average thickness is 1–20 nm. The dispersion is any one of anhydrous ethanol, isopropanol, acetone, and deionized water; The isocyanate dimer is one or more selected from hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, dicyclohexylmethane diisocyanate, and diphenylmethane diisocyanate; The organotin catalyst is one or more of dibutyltin dilaurate, stannous octoate, and stannous oleate.

[0018] Preferably, in step 1 of the above method, polyphenol amine-modified graphene nanosheets are prepared by modifying graphene nanosheets (GNP) with polyphenol amine (PPA) in the following manner: A graphene nanosheet (GNP) dispersion of 0.6–13 g / L was prepared and ultrasonically dispersed at 30–60 kHz for 0.5–4 h to form a graphene nanosheet suspension. Add 0.5–2 g / L phenol and 0.5–2 g / L amine to the graphene nanosheet suspension, and add 1–3 g / L tris(hydroxymethyl)aminomethane (Tris) to adjust the pH of the solution to 7–9. Set the stirring speed to 400–1000 r / min, and magnetically stir at a constant temperature of 20–40 °C for 2–8 h. Filter and dry the solution to obtain polyphenol amine modified graphene nanosheets, denoted as GNP@PPA. In the preparation of polyphenol amine modified graphene nanosheets in step 1 above, the average size of the unmodified graphene nanosheets GNP is 50-80 μm and the average thickness is 1-20 nm. The dispersion is any one of anhydrous ethanol, isopropanol, acetone or deionized water; The phenol is one or more of resorcinol, catechol, tea polyphenols, and tannic acid; The amine is one or more selected from dopamine hydrochloride, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentavinylhexylamine, ethylenediamine, o-phenylenediamine, and polyethyleneimine; The polymer obtained by reacting phenol and amine is polyphenolamine (PPA).

[0019] Preferably, in step 2 of the above method, the polyurethane prepolymer (i.e., PU) is prepared in the following manner: Under a nitrogen atmosphere, dehydrated polyether glycol was added to an organic solvent to prepare a solution of 40–80 g / L. Then, 10–30 g / L of isocyanate dimer DI and 0.2–0.5 wt% of organotin catalyst were added. The mechanical stirring speed was set to 500–1000 r / min, and the mixture was stirred at 60–110 °C for 2–4 h to prepare an isocyanate-terminated polyurethane prepolymer. Subsequently, 1–4 g / L butanediol and 1–3 g / L ureidopyrimidinone were added to the isocyanate-terminated polyurethane prepolymer. The stirring speed was set to 600–1000 r / min, and the mixture was mechanically stirred at 60–100 °C for 2–4 h to generate a polyurethane prepolymer containing urea, pyrimidinone, and carbamate groups. The system of polyurethane prepolymer containing urea, pyrimidinone and urethane groups was cooled to 40-50°C, and 0.05-0.5 g / L glycerol, 1-5 g / L diketoxime and 0.05-0.2 g / L metal chloride were added. The stirring speed was set to 600-1000 r / min, and the reaction was carried out for 2-4 h to obtain a polyurethane prepolymer containing oxime urethane bonds, hydrogen bonds and metal coordination bonds.

[0020] Preferably, in the preparation of the polyurethane prepolymer in step 2 above, the polyether diol is one or more of polytetrahydrofuran, polyethylene oxide diol, and polyethylene glycol; The organic solvent used is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), tetrahydrofuran (THF), and toluene. The isocyanate dimer is one or more selected from hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, dicyclohexylmethane diisocyanate, and diphenylmethane diisocyanate; The organotin catalyst mentioned above is one or more of dibutyltin dilaurate, stannous octoate, and stannous oleate; The ureidopyrimidinone is one or more of 2-ureido-4(1H)-pyrimidinone, 2,4-diamino-6-hydroxypyrimidinone, and methacrylated ureidopyrimidinone; The diketone dioxime is one or more selected from butanedione dioxime, 1,2-cyclohexanedione dioxime, diphenylethylenedione dioxime, and dimethyl ketone dioxime; The metal chloride is one or more of copper chloride, zinc chloride, and ferric chloride.

[0021] Preferably, in step 2 of the above method, the BNNS@DI obtained in step 1 is dispersed into a pre-prepared polyurethane prepolymer for in-situ polymerization, and then cast into a film to obtain a composite film of isocyanate dimer modified boron nitride nanosheets and polyurethane prepolymer, including: Add 5-50 wt% of isocyanate dimer-modified boron nitride nanosheets obtained in step 1 to a pre-prepared polyurethane prepolymer containing oxime carbamate bonds, hydrogen bonds, and metal coordination bonds. Set the stirring speed to 600-1000 r / min and react at 60-80℃ for 2-4 h to obtain a first polyurethane composite precursor. After cooling, pour the first polyurethane composite precursor into a polytetrafluoroethylene mold, place it at room temperature for 20-30 min, and then vacuum dry and cure it at 50-75℃ for 12-24 h. Then, hot press it at 60-120℃ and 5-20 MPa for 1-4 h to obtain a composite film of isocyanate dimer-modified boron nitride nanosheets and polyurethane prepolymer, denoted as BNNS@DI-PU film.

[0022] The thickness of the composite film of isocyanate dimer modified boron nitride nanosheets and polyurethane prepolymer obtained in step 2 above is 0.1 mm.

[0023] Preferably, in step 2 of the above method, the GNP@PPA obtained in step 1 is dispersed into a pre-prepared polyurethane prepolymer for in-situ polymerization, and then cast into a film to obtain a composite film of polyphenol amine modified graphene nanosheets and polyurethane prepolymer, including: Add 0.5–20 wt% of polyphenol amine-modified graphene nanosheets obtained in step 2 to a pre-prepared polyurethane prepolymer containing oxime carbamate bonds, hydrogen bonds, and metal coordination bonds. Set the stirring speed to 600–1000 r / min and react at 60–80 °C for 2–4 h to obtain a second polyurethane composite precursor. After cooling, pour the second polyurethane composite precursor into a polytetrafluoroethylene mold, place it at room temperature for 20–30 min, and then vacuum dry and cure it at 50–75 °C for 12–24 h. Then, hot press it at 60–120 °C and 5–20 MPa for 1–4 h to obtain a polyphenol amine-modified graphene nanosheet and polyurethane prepolymer composite film, denoted as GNP@PPA-PU film.

[0024] The thickness of the composite film of polyphenol amine modified graphene nanosheets and polyurethane prepolymer obtained in step 2 above is 0.1 mm.

[0025] Preferably, in step 3 of the above method, the BNNS@DI-PU film obtained in step 2 is used as the intermediate insulating layer, and the GNP@PPA-PU film is used as the upper and lower layers of the intermediate insulating layer, respectively, serving as upper and lower electromagnetic shielding layers. These layers are stacked to form a sandwich structure and then hot-pressed to obtain a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions, comprising: The BNNS@DI-PU film obtained in step 2 is used as the intermediate insulating layer, and the GNP@PPA-PU film is placed on the upper and lower layers respectively as the upper and lower electromagnetic shielding layers, forming a sandwich structure of GNP@PPA-PU / BNNS@DI-PU / GNP@PPA-PU. The mixture is then hot-pressed at 60-120℃ and 5-20MPa for 1-4 hours to obtain a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions, denoted as SWPU.

[0026] The thickness of the SWPU obtained in step 3 above is 0.1 mm.

[0027] According to the preparation process of this invention, the synthesized polyurethane composite material contains oxime carbamate bonds, metal coordination bonds, and hydrogen bonds, endowing the polyurethane composite material with excellent self-healing properties. Simultaneously, the isocyanate groups on the surface of BNNS@DI and the amino and hydroxyl groups on the surface of GNP@PPA can react with the functional groups on the polyurethane molecular chain, effectively enhancing the interfacial bonding force between the BNNS@DI and GNP@PPA fillers and the polyurethane matrix, and improving the dispersion of the fillers in the polymer matrix. Furthermore, because the intermediate insulating layer of BNNS@DI-PU blocks the formation of conductive channels between the upper and lower GNP@PPA-PU layers, it endows the polyurethane composite material with overall insulation properties. The above method, through molecular structure design, filler-matrix interface optimization, and composite material structure control, prepares a novel self-healing polyurethane composite material that simultaneously possesses excellent thermal conductivity and electromagnetic shielding functions while maintaining good insulation properties. This method has a simple preparation process, mild reaction conditions, and stable product quality, demonstrating its great application potential in fields such as electronic devices.

[0028] This invention provides a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions prepared by the above method. The composite material is made by using isocyanate dimer modified boron nitride nanosheets and polyurethane prepolymer composite film as the intermediate insulating layer, and placing polyphenol amine modified graphene nanosheets and polyurethane prepolymer composite film on the upper and lower layers of the intermediate insulating layer respectively as the upper and lower electromagnetic shielding layers. The self-healing polyurethane composite material is obtained by hot pressing after stacking to form a sandwich structure material.

[0029] To more clearly demonstrate the technical solution and its effects provided by the present invention, the following detailed description of the solution provided by the embodiments of the present invention is provided with reference to specific examples.

[0030] Example 1 This embodiment provides a self-healing polyurethane composite material that combines thermal conductivity and electromagnetic shielding functions. Its preparation method includes the following steps: Step 1: Prepare two types of nanosheets respectively: Step 11) Boron nitride nanosheets modified with isocyanate dimer were prepared to obtain isocyanate dimer modified boron nitride nanosheets, denoted as BNNS@DI; Specifically, 0.6g of unmodified hexagonal boron nitride (BN) was added to 100mL of isopropanol, ball-milled at 200r / min for 4h, and then centrifuged and vacuum-dried to form exfoliated hexagonal boron nitride nanosheets (BNNS). 0.6 g of exfoliated hexagonal boron nitride nanosheets (BNNS) were added to 100 mL of anhydrous ethanol, along with 0.05 g of dicyclohexylmethane diisocyanate (HMDI) and 1 mg of dibutyltin dilaurate (DBTDL). The stirring speed was set to 800 r / min, and the mixture was magnetically stirred at 70 °C for 4 h to form a BNNS@DI suspension. The suspension was then filtered and dried to obtain BNNS@DI. Step 12) Polyphenol amine modified graphene nanosheets were prepared by using polyphenol amine modified graphene nanosheets, denoted as GNP@PPA; Specifically, 0.06 g of graphene nanosheets (GNP) were added to 100 mL of anhydrous ethanol and ultrasonically dispersed at 60 kHz for 2 h to form a GNP suspension. 0.1 g of tea polyphenols and 0.1 g of dopamine hydrochloride were added to the GNP suspension, followed by 0.1 g of tris(hydroxymethyl)aminomethane (Tris) to adjust the pH to 9. The stirring speed was set to 600 r / min, and the mixture was reacted at a constant temperature of 30 °C for 3 h to form a GNP@PPA suspension. The GNP@PPA suspension was then filtered and dried to obtain GNP@PPA.

[0031] Step 2: First, prepare the polyurethane prepolymer (i.e., PU), then prepare two composite films separately: Step 21) The method for preparing the polyurethane prepolymer (i.e., PU) is as follows: Step 211) Add 4g of dehydrated polytetrahydrofuran PTMEG-2000, 1.94g of isophorone diisocyanate IPDI and 20mg of dibutyltin dilaurate DBTDL to 100mL of N,N-dimethylformamide DMF solution, set the stirring speed to 500r / min, and mechanically stir at 95℃ for 2h to obtain isocyanate-terminated polyurethane prepolymer; Step 212) Subsequently, 0.22 g of butanediol and 0.19 g of 2,4-diamino-6-hydroxypyrimidine were added to the isocyanate-terminated polyurethane prepolymer. The stirring speed was set to 800 r / min, and the mixture was mechanically stirred at 95 °C for 2 h to obtain a polyurethane prepolymer containing urea, pyrimidinone and urethane groups. Step 213) Cool the polyurethane prepolymer system containing urea, pyrimidinone and urethane groups from step 212 to 50°C, add 0.045g glycerol, 0.35g dimethylglyoxime and 13.4mg copper chloride, set the stirring speed to 800r / min, and react for 2h to obtain a polyurethane prepolymer containing oxime urethane bonds, hydrogen bonds and metal coordination bonds.

[0032] Step 22) The BNNS@DI obtained in step 11 is dispersed into the polyurethane prepolymer obtained in step 21 for in-situ polymerization, and then cast into a film to obtain a composite film of isocyanate dimer modified boron nitride nanosheets and polyurethane prepolymer, denoted as BNNS@DI-PU. Specifically, 0.6g of BNNS@DI obtained in step 11 is added to the polyurethane prepolymer solution obtained in step 21. The stirring speed is set to 1000r / min, and the reaction is carried out at 80℃ for 2h. After cooling, it is poured into a polytetrafluoroethylene mold, placed at room temperature for 30min, vacuum dried at 50℃ for 12h, and then hot-pressed at 120℃ and 5MPa for 1h to obtain a 0.1mm thick BNNS@DI-PU film.

[0033] Step 23) Disperse the GNP@PPA obtained in step 12 into the polyurethane prepolymer obtained in step 21 for in-situ polymerization, and then cast it into a film to obtain a composite film of polyphenol amine modified graphene nanosheets and polyurethane prepolymer, denoted as GNP@PPA-PU. Specifically, 0.06g of GNP@PPA obtained in step 12 is added to the polyurethane prepolymer solution obtained in step 21. The stirring speed is set to 1000r / min, and the reaction is carried out at 80℃ for 2h. After cooling, it is poured into a polytetrafluoroethylene mold, placed at room temperature for 30min, vacuum dried at 50℃ for 12h, and then hot-pressed at 120℃ and 5MPa for 1h to obtain a 0.1mm thick GNP@PPA-PU film. Step 3) Alternately stack the 0.1 mm thick BNNS@DI-PU film and the 0.1 mm thick GNP@PPA-PU film obtained in Step 2 above, with the middle layer being the BNNS@DI-PU film and the upper and lower layers being the GNP@PPA-PU films, to form a sandwich structure material. Hot press the sandwich structure material at 120℃ and 10MPa for 2 hours to obtain a 0.1 mm thick self-healing polyurethane composite material SWPU with both thermal conductivity and electromagnetic shielding functions.

[0034] The thermal conductivity, electromagnetic shielding efficiency, and volume resistivity of the polyurethane composite material prepared in Example 1 before and after self-healing were measured. The test results are shown in Tables 1 and 2.

[0035] Example 2 This embodiment provides a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions. The preparation method is the same as in Example 1, except that 0.1g of dicyclohexylmethane diisocyanate is added in step 11 of step 1, and 0.2g of tannic acid and 0.2g of tetraethylenepentamine are added in step 12. The thermal conductivity, electromagnetic shielding efficiency and volume resistivity of the prepared polyurethane composite material before and after self-healing are measured. The test results are shown in Table 1 and Table 2.

[0036] Example 3 This embodiment provides a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions. The preparation method is the same as in Example 1, except that 1.2g of isophorone isocyanate dimer is added in step 211, 0.1g of butanediol and 0.15g of 2,4-diamino-6-hydroxypyrimidine are added in step 212, and 0.12g of butanedione oxime and 6.9mg of zinc chloride are added in step 213. The thermal conductivity, electromagnetic shielding efficiency and volume resistivity of the prepared polyurethane composite material before and after self-healing are measured. The test results are shown in Tables 1 and 2.

[0037] Example 4 This embodiment provides a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions. The preparation method is the same as in Example 1, except that 2g of BNNS@DI is added in step 22. The thermal conductivity, electromagnetic shielding efficiency and volume resistivity of the prepared polyurethane composite material before and after self-healing are measured. The test results are shown in Table 1 and Table 2.

[0038] Example 5 This embodiment provides a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions. The preparation method is the same as in Example 1, except that 3.3g of BNNS@DI is added in step 22. The thermal conductivity, electromagnetic shielding efficiency and volume resistivity of the prepared polyurethane composite material before and after self-healing are measured. The test results are shown in Table 1 and Table 2.

[0039] Example 6 This embodiment provides a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions. The preparation method is the same as in Example 1, except that 3.3g of BNNS@DI is added in step 22 and 0.6g of GNP@PPA is added in step 23. The thermal conductivity, electromagnetic shielding efficiency and volume resistivity of the prepared polyurethane composite material before and after self-healing are measured. The test results are shown in Table 1 and Table 2.

[0040] Example 7 This embodiment provides a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions. The preparation method is the same as in Example 1, except that 3.3g of BNNS@DI is added in step 22 and 1.3g of GNP@PPA is added in step 23. The thermal conductivity, electromagnetic shielding efficiency and volume resistivity of the prepared polyurethane composite material before and after self-healing are measured. The test results are shown in Table 1 and Table 2.

[0041] Comparative Example 1 Three BNNS@DI-PU films prepared in step 22 of Example 1 were stacked and hot-pressed at 120℃ and 10MPa for 2 hours to obtain a BNNS@DI-PU film with a thickness of 0.1mm. The thermal conductivity, electromagnetic shielding efficiency, and volume resistivity of the prepared polyurethane composite material before and after self-healing were measured. The test results are shown in Tables 1 and 2.

[0042] Comparative Example 2 Three GNP@PPA-PU films prepared in step 23 of Example 1 were stacked and hot-pressed at 120℃ and 10MPa for 2 hours to obtain a GNP@PPA-PU film with a thickness of 0.1mm. The thermal conductivity, electromagnetic shielding efficiency, and volume resistivity of the prepared polyurethane composite material before and after self-healing were measured. The test results are shown in Tables 1 and 2.

[0043] Comparative Example 3 The polyurethane prepolymer obtained in step 213 of Example 1 was cooled and poured into a polytetrafluoroethylene mold. It was placed at room temperature for 30 minutes, vacuum dried at 50°C for 12 hours, and then hot-pressed at 120°C and 5 MPa for 1 hour to obtain a polyurethane film with a thickness of 0.1 mm. The thermal conductivity, electromagnetic shielding efficiency, and volume resistivity of the prepared polyurethane composite material before and after self-healing were measured. The test results are shown in Tables 1 and 2.

[0044] Comparative Example 4 In step 22 of Example 1, 0.6 g of unmodified boron nitride nanosheets (BNNS) were added to the polyurethane prepolymer obtained in step 21 to prepare a 0.1 mm thick BNNS-PU film. In step 23, 0.06 g of unmodified graphene nanosheets (GNP) were added to the polyurethane prepolymer obtained in step 21 to prepare a 0.1 mm thick GNP-PU film. The BNNS-PU film and the GNP-PU film were stacked alternately to form a sandwich structure material with a BNNS-PU film in the middle and GNP-PU films on the top and bottom. The sandwich structure material was hot-pressed at 120 °C and 10 MPa for 2 h to obtain a polyurethane composite material with a thickness of 0.1 mm. The thermal conductivity, electromagnetic shielding efficiency, and volume resistivity of the prepared polyurethane composite material before and after self-healing were measured. The test results are shown in Tables 1 and 2.

[0045] It is understood that the above comparative examples 1-4 were designed to evaluate the performance of the materials prepared by the present invention and do not belong to the prior art.

[0046] Performance testing: The in-plane and out-of-plane thermal conductivity of the materials obtained in Examples 1-7 and Comparative Examples 1-4 of the present invention were tested. A 3cm × 1cm polyurethane composite material was cut in the middle and then tightly bonded together. After heat treatment at 100℃ for 3 hours, the fracture surface disappeared, and the sample re-healed. The in-plane and out-of-plane thermal conductivity of the self-healing material were then tested using a LFA 467 Hyper Flash laser thermal conductivity meter. The test results are shown in Table 1 below.

[0047] Table 1 shows the test data for the in-plane and out-of-plane thermal conductivity of the materials in each embodiment and comparative example: .

[0048] Electromagnetic shielding efficiency and volume resistivity were tested on the materials obtained in Examples 1-7 and Comparative Examples 1-4 of the present invention. A 3cm × 1cm polyurethane composite material was cut in the middle and then tightly bonded together. After heat treatment at 100℃ for 3 hours, the fracture surface disappeared, and the sample re-healed. The electromagnetic shielding efficiency of the self-healing material was then tested using an N5244B microwave network analyzer. The test results are shown in Table 2 below. Table 2 shows the test data for the electromagnetic shielding efficiency and volume resistivity of the materials in each embodiment and comparative example: .

[0049] The test results above show that the polyurethane composite material prepared by the method in this embodiment of the invention has a volume resistivity of 1.83 × 10⁻⁶. 11 At Ω·m, the maximum in-plane thermal conductivity reaches 75.65 W·m. -1 ·K -1 The out-of-plane thermal conductivity reaches 74.33 W·m. -1 ·K -1 The electromagnetic shielding efficiency reaches 62.58dB, and the self-healing efficiency reaches 98%, indicating that it has excellent thermal conductivity and electromagnetic shielding performance, while maintaining good insulation and self-repairing performance.

[0050] It is worth noting that the contents not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

[0051] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of the present invention and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions, characterized in that, include: Step 1: Prepare two types of nanosheets respectively: Boron nitride nanosheets modified with isocyanate dimers were prepared. Boron nitride nanosheets modified with isocyanate dimers are prepared by the following method: Prepare an unmodified hexagonal boron nitride dispersion of 6–33 g / L, ball mill it at 200–800 r / min for 4–12 h, then centrifuge and vacuum dry it to form exfoliated hexagonal boron nitride nanosheets. Prepare a dispersion of exfoliated hexagonal boron nitride nanosheets at a concentration of 6–33 g / L. Add 0.1–1 g / L isocyanate dimer and 0.1–0.3 wt% organotin catalyst to the dispersion. Set the stirring speed to 600–1000 r / min and magnetically stir at a constant temperature of 20–80 °C for 2–4 h. After filtration and drying, the resulting isocyanate dimer-modified layered hexagonal boron nitride nanosheets are known as isocyanate dimer-modified boron nitride nanosheets. Polyphenol amine-modified graphene nanosheets were prepared using polyphenol amine-modified graphene nanosheets. Step 2: First, prepare the polyurethane prepolymer, then prepare two composite films separately: The polyurethane prepolymer is first prepared in the following manner, including: Under a nitrogen atmosphere, dehydrated polyether glycol is added to an organic solvent to prepare a solution of 40–80 g / L, then 10–30 g / L isocyanate dimer and 0.2–0.5 wt% organotin catalyst are added. The mechanical stirring speed is set to 500–1000 r / min, and the mixture is stirred at 60–110 °C for 2–4 h to obtain an isocyanate-terminated polyurethane prepolymer. Add 1-4 g / L butanediol and 1-3 g / L ureidopyrimidinone to the prepared isocyanate-terminated polyurethane prepolymer, set the stirring speed to 600-1000 r / min, and mechanically stir at 60-100℃ for 2-4 h to generate a polyurethane prepolymer containing urea, pyrimidinone and urethane groups. The polyurethane prepolymer system containing urea, pyrimidinone and urethane groups was cooled to 40-50°C, and 0.05-0.5 g / L glycerol, 1-5 g / L diketoxime and 0.05-0.2 g / L metal chloride were added. The stirring speed was set to 600-1000 r / min, and the reaction was carried out for 2-4 h to obtain a polyurethane prepolymer containing oxime urethane bonds, hydrogen bonds and metal coordination bonds. The isocyanate dimer modified boron nitride nanosheets obtained in step 1 are dispersed into the prepared polyurethane prepolymer for in-situ polymerization, and then cast into a film to obtain a composite film of isocyanate dimer modified boron nitride nanosheets and polyurethane prepolymer. The polyphenol amine modified graphene nanosheets obtained in step 1 are dispersed into the prepared polyurethane prepolymer for in-situ polymerization, and then cast into a film to obtain a composite film of polyphenol amine modified graphene nanosheets and polyurethane prepolymer. Step 3: The isocyanate dimer-modified boron nitride nanosheets and polyurethane prepolymer composite film prepared in Step 2 are used as the intermediate insulating layer. The polyphenol amine-modified graphene nanosheets and polyurethane prepolymer composite film are placed on the upper and lower layers of the intermediate insulating layer, respectively, as the upper electromagnetic shielding layer and the lower electromagnetic shielding layer. After stacking to form a sandwich structure, they are hot-pressed to obtain a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions.

2. The method for preparing the self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions according to claim 1, characterized in that, In step 1, polyphenol-modified graphene nanosheets are prepared using polyphenol-modified graphene nanosheets in the following manner: Prepare a dispersion of unmodified graphene nanosheets at a concentration of 0.6–13 g / L, and ultrasonically disperse it at 30–60 kHz for 0.5–4 h to form a graphene nanosheet suspension. Add 0.5–2 g / L phenol and 0.5–2 g / L amine to the graphene nanosheet suspension, and add 1–3 g / L tris(hydroxymethyl)aminomethane to adjust the pH of the solution to 7–9. Set the stirring speed to 400–1000 r / min, and magnetically stir at a constant temperature of 20–40 °C for 2–8 h. After filtration and drying, the obtained polyphenol amine modified graphene nanosheets are called polyphenol amine modified graphene nanosheets.

3. The method for preparing the self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions according to claim 2, characterized in that, In the preparation of isocyanate dimer-modified boron nitride nanosheets in step 1, the average size of the unmodified hexagonal boron nitride is 1-60 μm and the average thickness is 1-20 nm. The dispersion is any one of anhydrous ethanol, isopropanol, acetone and deionized water; The isocyanate dimer is one or more selected from hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, dicyclohexylmethane diisocyanate, and diphenylmethane diisocyanate; The organotin catalyst is one or more of dibutyltin dilaurate, stannous octoate, and stannous oleate. In step 1, the unmodified graphene nanosheets have an average size of 50–80 μm and an average thickness of 1–20 nm. The dispersion is any one of anhydrous ethanol, isopropanol, acetone and deionized water; The phenol is one or more of resorcinol, catechol, tea polyphenols, and tannic acid; The amine is one or more selected from dopamine hydrochloride, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentavinylhexylamine, ethylenediamine, o-phenylenediamine, and polyethyleneimine; The polymer obtained by reacting phenol and amine is polyphenolamine.

4. The method for preparing the self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions according to claim 1, characterized in that, In step 2, the polyurethane prepolymer is prepared using one or more of polytetrahydrofuran, polyethylene oxide glycol, and polyethylene glycol. The organic solvent is one or more selected from N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), tetrahydrofuran (THF), and toluene. The isocyanate dimer is one or more selected from hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, dicyclohexylmethane diisocyanate, and diphenylmethane diisocyanate; The organotin catalyst is one or more of dibutyltin dilaurate, stannous octoate, and stannous oleate. The ureidopyrimidinone is one or more of 2-ureido-4(1H)-pyrimidinone, 2,4-diamino-6-hydroxypyrimidinone and methacrylated ureidopyrimidinone; The diketone dioxime is one or more selected from butanedione dioxime, 1,2-cyclohexanedione dioxime, diphenylethylenedione dioxime, and dimethyl ketone dioxime; The metal chloride is one or more of copper chloride, zinc chloride, and ferric chloride.

5. The method for preparing a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions according to claim 1 or 4, characterized in that, In step 2, the isocyanate dimer-modified boron nitride nanosheets obtained in step 1 are dispersed into the pre-prepared polyurethane prepolymer for in-situ polymerization, and then cast into a film to obtain a composite film of isocyanate dimer-modified boron nitride nanosheets and polyurethane prepolymer, comprising: Add 5-50 wt% of isocyanate dimer-modified boron nitride nanosheets obtained in step 1 to a pre-prepared polyurethane prepolymer containing oxime carbamate bonds, hydrogen bonds, and metal coordination bonds. Set the stirring speed to 600-1000 r / min and react at 60-80℃ for 2-4 h to obtain a first polyurethane composite precursor. After cooling, pour the first polyurethane composite precursor into a polytetrafluoroethylene mold, place it at room temperature for 20-30 min, and then vacuum dry and cure it at 50-75℃ for 12-24 h. Then, hot press it at 60-120℃ and 5-20 MPa for 1-4 h to obtain a composite film of isocyanate dimer-modified boron nitride nanosheets and polyurethane prepolymer. In step 2, the polyphenol amine-modified graphene nanosheets obtained in step 1 are dispersed into the pre-prepared polyurethane prepolymer for in-situ polymerization, and then cast into a film to obtain a composite film of polyphenol amine-modified graphene nanosheets and polyurethane prepolymer, comprising: Add 0.5–20 wt% of the polyphenol amine-modified graphene nanosheets obtained in step 1 to a pre-prepared polyurethane prepolymer containing oxime carbamate bonds, hydrogen bonds, and metal coordination bonds. Set the stirring speed to 600–1000 r / min and react at 60–80 °C for 2–4 h to obtain a second polyurethane composite precursor. After cooling, pour the second polyurethane composite precursor into a polytetrafluoroethylene mold, place it at room temperature for 20–30 min, and then vacuum dry and cure it at 50–75 °C for 12–24 h. Then, hot press it at 60–120 °C and 5–20 MPa for 1–4 h to obtain a composite film of polyphenol amine-modified graphene nanosheets and polyurethane prepolymer.

6. The method for preparing the self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions according to claim 1, characterized in that, In step 2, the thickness of the composite film of isocyanate dimer modified boron nitride nanosheets and polyurethane prepolymer is 0.1 mm. The thickness of the obtained polyphenol amine modified graphene nanosheet and polyurethane prepolymer composite film is 0.1 mm.

7. The method for preparing a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions according to any one of claims 1-6, characterized in that, In step 3, the isocyanate dimer-modified boron nitride nanosheets and polyurethane prepolymer composite film obtained in step 2 are used as an intermediate insulating layer. The polyphenol amine-modified graphene nanosheets and polyurethane prepolymer composite film are placed on the upper and lower layers of the intermediate insulating layer, respectively, as the upper and lower electromagnetic shielding layers. After stacking to form a sandwich structure, they are hot-pressed to obtain a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions, including: The isocyanate dimer-modified boron nitride nanosheets and polyurethane prepolymer composite film obtained in step 2 are used as the intermediate insulating layer. The polyphenol amine-modified graphene nanosheets and polyurethane prepolymer composite film are placed on the upper and lower layers of the intermediate insulating layer, respectively, as the upper and lower electromagnetic shielding layers. This forms a sandwich structure material with two layers of polyphenol amine-modified graphene nanosheets and polyurethane prepolymer composite films and a middle layer of isocyanate dimer-modified boron nitride nanosheets and polyurethane prepolymer composite film. The sandwich structure material is hot-pressed at 60-120℃ and 5-20MPa for 1-4 hours to obtain a self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions.

8. The method for preparing the self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions according to claim 7, characterized in that, The thickness of the self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions is 0.1 mm.

9. A self-healing polyurethane composite material with both thermal conductivity and electromagnetic shielding functions, prepared by the method according to any one of claims 1-8, characterized in that, This composite material is a self-healing polyurethane composite material made by stacking isocyanate dimer modified boron nitride nanosheets and polyurethane prepolymer composite film as the middle insulating layer, and placing polyphenol amine modified graphene nanosheets and polyurethane prepolymer composite film on the upper and lower layers of the middle insulating layer as the upper and lower electromagnetic shielding layers, respectively.