Hot glue for composite material and preparation method thereof

Abstract

The invention belongs to the technical field of polymer composite heat conduction materials, and particularly relates to a hot adhesive for a composite material and a preparation method thereof. The method aims at solving the problem that current thermal conductivity improvement generally depends on a sacrifice process and adhesion. A three-dimensional heat conduction network is constructed through surface modification and magnetic field induced orientation of the perylene modifier on graphene, the perylene modifier is firmly adsorbed on the surface of the graphene through pi-pi accumulation and forms a dynamic covalent and chemical bonding interface with a hyperbranched polysiloxane matrix, and meanwhile, the surface of the modified graphene is loaded with nano-scale magnetic particles, so that the surface of the modified graphene is subjected to surface modification and magnetic field induced orientation. Under the action of a magnetic field, orientation is performed to form a three-dimensional heat-conducting chain structure, so that good flowability and adhesive force are still realized under relatively high filler loading, and the heat conductivity coefficient is improved.

Description

A hot adhesive for composite materials and its preparation method Technical Field

[0001] This invention belongs to the field of polymer composite thermally conductive materials technology, specifically relating to a thermal adhesive for composite materials and its preparation method. Background Technology

[0002] With the increasing integration and power density of electronic devices, the demand for efficient heat dissipation materials is becoming increasingly urgent. Traditional electronic packaging often uses silicone adhesive as a potting compound or binder (CN115505367A) to protect components and conduct heat due to its excellent electrical insulation and flexibility.

[0003] However, conventional thermally conductive adhesives currently face a dilemma: to achieve higher thermal conductivity, a large amount of highly thermally conductive ceramic powder is usually required to fill the organic matrix. However, a high filling rate significantly increases the viscosity of the system, reduces processability, and may weaken the interfacial adhesion between the matrix and the filler. Poor filler dispersion and weak interfacial bonding often lead to high interfacial thermal resistance, limiting the effective conduction of heat in adhesive composites. Although efforts have been made to improve the interface through measures such as modifying fillers with surface coupling agents, achieving a balance between high thermal conductivity, low viscosity, and high bond strength remains extremely difficult.

[0004] Graphene is considered an ideal high-thermal-conductivity filler due to its extremely high intrinsic thermal conductivity. Compared to traditional spherical or granular fillers, graphene sheets have a high aspect ratio and a two-dimensional layered structure, which can create efficient heat conduction pathways in composite materials. However, graphene is prone to agglomeration and sedimentation in resins, leading to obstruction of effective heat conduction pathways and deterioration of the mechanical properties of composite materials. This is mainly attributed to the strong π-π interactions and van der Waals forces between graphene sheets, making it difficult to stably disperse in the matrix. Boron nitride (BN) is widely used as a filler in thermally conductive composite materials due to its high thermal conductivity and intrinsic electrical insulation. In particular, hexagonal boron nitride (h-BN) has a layered structure and anisotropic thermal conductivity similar to graphite, exhibiting excellent in-plane thermal conductivity but poor vertical thermal conductivity. However, by preparing BN into spherical microspheres, the anisotropy can be mitigated to some extent and its packing performance in the matrix can be improved. Thermally conductive adhesives that use only BN filler usually require a high volume fraction to achieve the desired thermal conductivity, and the interface between BN and the silicone matrix is ​​relatively inert, resulting in a relatively large interfacial thermal resistance.

[0005] In summary, while existing technologies seek to improve the thermal conductivity of thermally conductive adhesives, they often result in a decrease in processability or adhesion performance, making it difficult to balance all aspects of performance. There is an urgent need for a preparation method that can significantly improve the thermal conductivity of adhesives without sacrificing processability and adhesion. Summary of the Invention

[0006] This invention provides a hot adhesive for composite materials and its preparation method. By modifying graphene and loading it with magnetic nanoparticles, a certain proportion of the magnetic graphene is mixed with insulating boron nitride microspheres. During the curing process of the adhesive, a magnetic field is applied to orient the filler to form a three-dimensional thermally conductive network structure, thereby endowing the adhesive with extremely high thermal conductivity and good electrical insulation.

[0007] The specific technical solution is as follows: A method for preparing a hot adhesive for composite materials, as follows: S1: Preparation of modified graphene.

[0008] S11: Add graphene powder to N-methylpyrrolidone and sonicate in an ice-water bath to obtain a graphene suspension.

[0009] S12: The perylene modifier is mixed with N-methylpyrrolidone and then added to the graphene suspension prepared in S11. The mixture is stirred, centrifuged, washed, dried, and ground to obtain modified graphene.

[0010] S2: Magnetic modified graphene; S21: Dissolve the modified graphene prepared in S12 in deionized water, add sodium dodecyl sulfate, and obtain a modified suspension.

[0011] S22: Add mixed iron salts to the modified suspension prepared in S21, stir, adjust the pH to 10, then use a magnet to collect the product, wash, dry, and obtain magnetic modified graphene.

[0012] S3: Hot glue preparation.

[0013] S31: Dissolve hyperbranched polysiloxane resin in methyl ethyl ketone solvent, then add magnetic modified graphene and spherical boron nitride prepared in S22, stir, and obtain a suspension.

[0014] S32: The suspension prepared in S31 is magnetically induced and stirred, vacuum degassed, then coated on the surface of the composite material, heated and cured to obtain a cured thermally conductive adhesive.

[0015] Furthermore, the ultrasonic treatment described in S11 has the following parameter settings: power 500-700W, on for 2s / off for 1s, duration 0.5-1.5h.

[0016] The graphene suspension described in S11 has a concentration of 3 to 8 mg / mL.

[0017] Furthermore, the perylene modifier described in S12 has a mass ratio of 1:5 to 1:10 with graphene.

[0018] The stirring described in S12 has the following parameters: temperature 50-70℃, speed 400-600rpm, and duration 3-5h.

[0019] The centrifugation described in S12 has the following parameters: rotation speed 8000 rpm, duration 15 min.

[0020] The drying process described in S12 has the following parameters: temperature 60℃, duration 12h.

[0021] Furthermore, the sodium dodecyl sulfate described in S21 has a mass ratio of 1:10 to the modified graphene.

[0022] The mixed iron salt described in S22 is a mixture of ferric chloride and ferrous chloride, wherein the molar ratio of ferric chloride to ferrous chloride is 2:1, and the mass ratio of the mixed iron salt to modified graphene is 5:1.

[0023] Furthermore, the stirring described in S31 has the following parameter settings: temperature 50-70℃, rotation speed 200-400rpm, and duration 20-40min.

[0024] The suspension described in S31 has a hyperbranched polysiloxane resin solution concentration of 40-60%, and the total amount of filler added is 30-50% of the mass of the hyperbranched polysiloxane resin. Among them, the proportion of magnetically modified graphene is 60-80% of the total amount of filler added, and the proportion of spherical boron nitride is 20-40% of the total amount of filler added.

[0025] The magnetic field induction described in S32 has the following parameters: intensity 0.1-0.5T, duration 10-30min.

[0026] The stirring described in S32 has the following parameters: rotation speed 50-150 rpm, duration 10-30 min.

[0027] The vacuum degassing described in S32 has the following parameter settings: temperature 40℃, vacuum degree -0.095MPa, and duration 20-40min.

[0028] The temperature-curing process described in S32 has the following parameters: temperature 80-120℃, duration 1-3h.

[0029] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention solves the problems of dispersion and interface bonding by modifying graphene, thereby improving thermal conductivity and mechanical properties.

[0030] 2. This invention ensures the adhesion of the adhesive layer to the substrate through the dual interface combination of dynamic covalent bonds and solidified chemical bonds. Attached Figure Description

[0031] Figure 1 is a flow chart of a hot adhesive for composite materials and its preparation process.

[0032] Figure 2 is a flowchart of the preparation process of perylene modifier.

[0033] Figure 3 is a comparison of the thermal conductivity and viscosity data of the thermal adhesives prepared in Examples 1-4 and Comparative Examples 1-3.

[0034] Figure 4 shows the Raman spectra of the original graphene and the modified graphene in Example 1.

[0035] Figure 5 is the 1H NMR spectrum of intermediate 2 in Example 1.

[0036] Figure 6 is the proton NMR spectrum of the final product in Example 1.

[0037] Figure 7 is the mass spectrum of the final product in Example 1.

[0038] Figure 8 is the 1H NMR spectrum of intermediate 1 in Example 1.

[0039] Figure 9 is the 1H NMR spectrum of intermediate 3 in Example 1. Detailed Implementation

[0040] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0041] This invention proposes a hot adhesive for composite materials and its preparation method. As shown in Figure 1, it is a flowchart of the preparation method of a hot adhesive for composite materials. The detailed technical solution is as follows: 1. Raw material modification: Graphene powder is added to N-methylpyrrolidone and ultrasonically treated in an ice-water bath to obtain a graphene suspension; a perylene-perylene modifier (1,6,7,12-tetrahydro-9,10-bis[(4-bromophenyl)phenyl]perylene[9,10-d]pyran-3,4:9,10-dioxide-10,10-bis[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)butyl]dimethylammonium inner salt) is mixed with N-methylpyrrolidone, and then stirred, centrifuged, washed, dried and ground in the graphene suspension to obtain modified graphene.

[0042] The perylene modifier and its preparation process are shown in Figure 2, and are as follows: Synthesis of intermediate 1: In an anhydrous and oxygen-free environment, 1,6,7,12-tetrabromoperylene anhydride (10.0 mmol) was mixed and stirred with strictly dehydrated N,N-dimethylformamide (DMF, 50 mL), and then 30 mmol of (3-aminopropyl)triethoxysilane (APTES, with the temperature controlled not exceeding 30 °C and the amount added being 3 times the molar amount of dianhydride) was added dropwise, followed by anhydrous zinc acetate (5 mmol). The mixture was heated to 90 °C and kept at that temperature for 24 h, cooled to room temperature, sieved (200 mesh sieve), rotary evaporated, and anhydrous n-hexane (150 mL) was added to precipitate. At this time, a large amount of reddish-brown solid was observed to rapidly precipitate. The mixture was filtered and vacuum dried (60 °C, 12 h) to obtain the silanized tetrabromoperylene diimide intermediate.

[0043] Preparation of Intermediate 2: Under nitrogen protection, intermediate 1 (5 mmol), a very high excess of 4-bromophenylboronic acid (45 mmol, 9.0 equivalent), tetrakis(triphenylphosphine)palladium (Pd(PPh3)4, 0.6 mmol, 12 mol% of the amount of intermediate 1 mole), and anhydrous K2CO3 (50.0 mmol) were mixed, and then degassed anhydrous tetrahydrofuran (THF, 80 mL) was added through a syringe. A very small amount of water was then added, and the mixture was heated to 75 °C and reacted for 14 h to carry out a cross-coupling reaction. The mixture was then filtered under reduced pressure using diatomaceous earth, washed, rotary evaporated, and purified by silica gel column chromatography (the eluent was a mixture of dichloromethane and petroleum ether in a specific ratio) to obtain a pure PDI precursor containing four 4-bromophenyl groups (intermediate 2).

[0044] Transformation of intermediate 3: Under nitrogen protection, intermediate 2, excess bis(pinacolyl)diboron (B2pin2, 18.0 mmol, 9.0 equivalent), 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride catalyst (Pd(dppf)Cl2, 0.2 mmol, 10 mol%), and anhydrous K2CO3 (20 mL) were added, followed by degassed anhydrous DMF (40 mL). The mixture was sealed and heated to 85 °C, stirred for 24 h, cooled to room temperature, purified (added to a palladium removal agent containing functionalized silica (3 g), and shaken at room temperature for 4 h), filtered, and recrystallized to obtain pure intermediate 3 with pinacolyl borate ester groups.

[0045] Synthesis of perylene-modifying agent: The recrystallized and dried intermediate 3 (1.0 mmol) was dissolved in anhydrous acetonitrile (MeCN, 30 mL), and excess iodomethane (CH3I, 15.0 mmol, 15 equivalents) was added under ice-water bath. The mixture was sealed and heated to 70 °C and kept at that temperature for 36 h. After cooling to room temperature, excess acetone was added as an anti-precipitant. The mixture was centrifuged (8000 rpm, 10 min), washed, centrifuged again, and dried to obtain the perylene-modifying agent.

[0046] Utilizing the rigid, large planar structure of the perylene modifier, it adheres non-covalently to the graphene surface through strong π-π conjugation, much like a plaster. This force effectively avoids the damage to the graphene lattice structure that covalent modification might cause. Furthermore, due to the presence of quaternary ammonium cations in the perylene modifier, positively charged sites are formed on the graphene surface in appropriate solvent systems. Since all modified graphene sheets carry the same charge, electrostatic repulsion occurs between them, effectively resisting face-to-face re-agglomeration caused by van der Waals forces. This ensures dispersion stability during storage and subsequent processing. The silanoxy groups at the ends of the perylene modifier can react with the hydroxyl or amino groups in the hyperbranched polysiloxane resin during future thermosetting to form strong chemical bonds (siloxane bonds), thus creating a robust interface between the filler and the matrix.

[0047] 2. Magnetic Addition: The modified graphene was dissolved in deionized water, sodium dodecyl sulfate was added to obtain a modified suspension, then mixed iron salts were added, the mixture was stirred, the pH was adjusted to 10, and the product was collected by attracting with a magnet, washed, and dried to obtain magnetically modified graphene.

[0048] The iron salt is fully dissolved and comes into contact with the graphene surface. Ammonia solution is added dropwise to adjust the pH to 10. During this process, ferrous and ferric ions undergo a co-precipitation reaction, generating Fe3O4 magnetic nanoparticles in situ on the graphene surface.

[0049] 3. Preparation of thermal adhesive: Hyperbranched polysiloxane resin is dissolved in methyl ethyl ketone solvent, then magnetically modified graphene and spherical boron nitride are added and stirred to obtain a suspension. The suspension is then subjected to magnetic field induction and stirring, vacuum degassing, and then coated onto the surface of the composite material. The mixture is then heated and cured to obtain a cured thermally conductive adhesive.

[0050] Magnetically modified graphene exhibits a rigid, large-planar structure that is firmly adsorbed onto the graphene through π-π stacking. Quaternary ammonium cations provide electrostatic repulsion to prevent aggregation, while the terminal silane groups act as "chemical anchors," forming strong and reversible interfacial chemical bonds with the hydroxyl or amino groups of the hyperbranched polysiloxane resin during curing, significantly improving interfacial bonding and filler dispersibility. A hybrid filler system of "magnetized modified graphene and insulating spherical boron nitride microspheres" is employed. Under the induction of an external magnetic field, the magnetically anisotropic modified graphene connects end-to-end along the magnetic field lines, forming a continuous three-dimensional thermally conductive chain. The spherical boron nitride fills the gaps between the chains, preventing the thermally conductive chain from being disrupted and providing insulation, ultimately synergistically increasing thermal conductivity.

[0051] Example 1: A method for preparing a hot adhesive for composite materials, as follows: Table 1: Main raw materials

[0052] S1: Preparation of modified graphene.

[0053] S11: 6g of graphene powder was added to N-methylpyrrolidone and sonicated in an ice-water bath to obtain a graphene suspension with a concentration of 6mg / mL. The sonication parameters were set as follows: power 600W, on for 2s / off for 1s, duration 1h.

[0054] S12: The perylene modifier was mixed with N-methylpyrrolidone and then added to the graphene suspension prepared in S11. The mixture was stirred, centrifuged at 8000 rpm for 15 min, washed three times with anhydrous ethanol, dried at 60℃ for 12 h, and ground to obtain modified graphene. The mass ratio of perylene modifier to graphene was 1:8, and the stirring parameters were set as follows: temperature 60℃, rotation speed 500 rpm, and stirring time 4 h.

[0055] S2: Magnetic modified graphene; S21: Dissolve the modified graphene prepared in S12 in deionized water, add sodium dodecyl sulfate, and obtain a modified suspension. The mass ratio of sodium dodecyl sulfate to modified graphene is 1:10. S22: Add mixed iron salt to the modified suspension prepared in S21, stir, adjust the pH to 10, then collect the product using a magnet, wash, and dry to obtain magnetic modified graphene. The mixed iron salt is a mixture of ferric chloride and ferrous chloride, with a molar ratio of ferric chloride to ferrous chloride of 2:1, and a mass ratio of the mixed iron salt to modified graphene of 5:1.

[0056] S3: Hot glue preparation.

[0057] S31: Hyperbranched polysiloxane resin is dissolved in methyl ethyl ketone (MEK) solvent, then the magnetically modified graphene and spherical boron nitride prepared in S22 are added, and the mixture is stirred to obtain a suspension. The stirring parameters are set as follows: temperature 60℃, rotation speed 300 rpm, and stirring time 30 min. The concentration of the hyperbranched polysiloxane resin solution in the suspension is 50%, and the total amount of filler added is 40% of the mass of the hyperbranched polysiloxane resin. Specifically, the proportion of magnetically modified graphene is 70% of the total filler added, and the proportion of spherical boron nitride is 30% of the total filler added.

[0058] S32: The suspension prepared in S31 was subjected to magnetic field induction and stirring, vacuum degassing, and then coated onto the surface of the composite material. It was then heated and cured to obtain a cured thermally conductive adhesive. The magnetic field induction intensity was 0.3T for 20 minutes; the stirring speed was 100 rpm for 20 minutes; the vacuum degassing parameters were: temperature 40℃, vacuum degree -0.095MPa for 30 minutes; and the heating and curing parameters were: temperature 100℃ for 2 hours.

[0059] Example 2 follows the same composition and preparation process as Example 1, except that in step S11 of the preparation process, the ultrasonic treatment power is 500W, the on-time is 2s and the off-time is 1s, and the duration is 0.5h. The other steps are the same.

[0060] In the preparation process, the concentration of graphene suspension in S11 is 3 mg / mL, and the other components are the same.

[0061] In the preparation process, the mass ratio of perylene modifier to graphene in S12 is 1:5, and other components are the same.

[0062] In step S12 of the preparation process, the stirring temperature is 50℃, the stirring speed is 400rpm, and the duration is 3h. Other steps are the same.

[0063] In step S31 of the preparation process, the stirring temperature is 50℃, the stirring speed is 200rpm, and the stirring time is 20min. Other steps are the same.

[0064] In the S31 preparation process, the suspension has a hyperbranched polysiloxane resin solution concentration of 40%, and the total amount of filler added is 30% of the mass of the hyperbranched polysiloxane resin. Among them, the proportion of magnetic modified graphene is 60% of the total amount of filler added, the proportion of spherical boron nitride is 40% of the total amount of filler added, and the other components are the same.

[0065] In the preparation process S32, the magnetic field induction intensity is 0.1T, the duration is 10min; the stirring speed is 50rpm, the duration is 10min; the vacuum degassing time is 20min; the curing temperature is 80℃, the duration is 1h, and the other steps are the same.

[0066] In step S2 of the preparation process, the other steps are the same.

[0067] Example 3 follows the same composition and preparation process as Example 1, except that: in step S11 of the preparation process, the ultrasonic treatment power is 700W, the on-time is 2s and the off-time is 1s, and the duration is 1.5h. The other steps are the same.

[0068] In the preparation process, the concentration of graphene suspension in S11 is 8 mg / mL, and the other components are the same.

[0069] In the preparation process S12, the mass ratio of perylene modifier to graphene is 1:10, and other components are the same.

[0070] In the preparation process S12, the stirring temperature is 70℃, the stirring speed is 600rpm, and the duration is 5h. Other steps are the same.

[0071] In step S31 of the preparation process, the stirring temperature is 70℃, the stirring speed is 400rpm, and the stirring time is 40min. Other steps are the same.

[0072] In the S31 preparation process, the suspension has a hyperbranched polysiloxane resin solution concentration of 60%, and the total amount of filler added is 50% of the mass of the hyperbranched polysiloxane resin. Among them, the proportion of magnetically modified graphene is 80% of the total amount of filler added, the proportion of spherical boron nitride is 20% of the total amount of filler added, and the other components are the same.

[0073] In the preparation process S32, the magnetic field induction intensity is 0.5T, the duration is 30min; the stirring speed is 150rpm, the duration is 30min; the vacuum degassing time is 40min; and the curing is carried out at a temperature of 120℃ for 3h. Other steps are the same.

[0074] Example 4 follows the same composition and preparation process as Example 1, except that: in step S11 of the preparation process, the ultrasonic treatment power is 550W, the on-time is 2s and the off-time is 1s, and the duration is 1.2h. The other steps are the same.

[0075] In the preparation process, the concentration of graphene suspension in S11 is 4 mg / mL, and the other components are the same.

[0076] In the preparation process, the mass ratio of perylene modifier to graphene in S12 is 1:6, and other components are the same.

[0077] In the preparation process S12, the stirring temperature was 66℃, the stirring speed was 550rpm, and the time was 3.5h. Other steps were the same.

[0078] In step S31 of the preparation process, the stirring temperature is 54℃, the stirring speed is 260rpm, and the stirring time is 37min. Other steps are the same.

[0079] In the S31 preparation process, the suspension has a hyperbranched polysiloxane resin solution concentration of 55%, and the total amount of filler added is 45% of the mass of the hyperbranched polysiloxane resin. Among them, the proportion of magnetic modified graphene is 75% of the total amount of filler added, the proportion of spherical boron nitride is 25% of the total amount of filler added, and the other components are the same.

[0080] In the preparation process S32, the magnetic field induction intensity is 0.4T, the duration is 15min; the stirring speed is 75rpm, the duration is 25min; the vacuum degassing time is 25min; the curing temperature is 110℃, the duration is 1.5h, and other steps are the same.

[0081] Comparative Example 1 follows the same composition and preparation process as Example 1, except that in step S12 of the preparation process, perylene modifier is not used to modify the graphene, while the other steps are the same.

[0082] Comparative Example 2 follows the same composition and preparation process as Example 1, except that boron nitride microspheres are removed in step S31 of the preparation process, and only modified graphene is used, while the other steps are the same.

[0083] Comparative Example 3 follows the same composition and preparation process as Example 1, except that no magnetic field induction is applied in step S32 of the preparation process, while the other steps are the same.

[0084] Samples of the original graphene and modified graphene from Example 1 were taken and Raman spectroscopy tests were performed (wavelength 532 nm, grating 1800 g / mm, spectral scanning range 1000–3200 cm⁻¹). -1 As shown in Figure 4, at 1350cm -1 The D peak, representing defect density, is located at 1580 cm⁻¹. -1 The G peak, representing the in-plane vibrations of graphene, shows a consistent intensity ratio between the modified and original graphene, indicating that the non-covalent modification by the perylene modifier avoids damage to the graphene conjugated system. In the spectrum, the G peak of the modified graphene shows a certain shift relative to the original graphene. This is because the perylene modifier, after adsorption on the graphene surface, induces a shift in the graphene band structure, resulting in a doping effect. For the modified graphene, the G peak at 1280 cm⁻¹... -1 and 1300cm -1 Two distinct new peaks appeared, namely the CH bending vibration of the perylene derivative or the stretching vibration of the perylene ring skeleton. This is because the mass ratio of the modifier to graphene reached 1:8, forming a dense adsorption layer on the graphene surface. With the help of graphene, the Raman scattering ability was enhanced, which significantly amplified the originally weak molecular signal, proving that the modifier was anchored on the graphene surface.

[0085] Samples of the intermediate and final products prepared in Example 1 were taken and subjected to proton nuclear magnetic resonance (NMR) spectroscopy. 1Figure 5 (intermediate 2, product after Suzuki reaction), Figure 6 (final product), Figure 8 (intermediate 1), and Figure 9 (intermediate 3) show the following peaks in Figure 5 (H spectrum, 32 scans): δ 2.50 ppm is the residual peak of the incompletely deuterated solvent of DMSO-d6; the peak around δ 3.3 ppm is the water peak; δ 8.61 represents the four symmetrical aromatic hydrogens on the perylene ring skeleton; δ 7.62–7.40 represents aromatic protons on substituents; multiple sets of multiple peaks exist between δ 4.17 and 3.33, representing methylene protons connected to heteroatoms; and peaks in the high-field regions at δ 1.57, 0.97, and 0.46 represent methyl or methylene groups at the alkyl chain ends. Figure 6 also shows the DMSO-d6 peak and water peak at δ 2.50 ppm and δ 3.3 ppm, respectively, with the perylene ring skeleton proton at δ 8.81.Compared to the intermediate's 8.61 ppm, the peak position shifts to a lower field, which is usually due to the quaternization reaction. The strong electron-withdrawing effect leads to proton deshielding. The aromatic hydrogens on the benzene ring substituents in the δ 7.90–7.23 range are affected by changes in molecular structure, resulting in regular changes in splitting and chemical shifts. The methylene protons attached to the quaternary ammonium nitrogen or oxygen atoms in the δ 3.65–3.33 range are present. Strong and sharp singlets and multiplets appear in the δ 1.50–0.63 range, which correspond to the terminal silaneoxy or bulky alkyl structures introduced in the modifier structure. In Figure 8, δ 8. The 18 ppm peak represents the four aromatic hydrogen atoms on the perylene ring skeleton. The 3.95 ppm peak represents the methylene hydrogen directly bonded to the nitrogen atom of the imide group, originating from the strong electron-withdrawing effect of the nitrogen atom in the imide group and the adjacent carbonyl group, causing the proton's chemical shift to move to a lower field. The 3.82 ppm peak represents the methylene hydrogen in the siloxane terminal group, directly bonded to the oxygen atom, exhibiting a deshielding effect, thus appearing around 3.8 ppm. Simultaneously, it is coupled by the three hydrogens on the adjacent methyl group, splitting into a typical quartet. The 1.79 ppm peak represents the methylene hydrogen in the middle of the propyl linkage chain, and the 1.21 ppm peak represents... The triplet peak is due to the coupling of the terminal methyl hydrogen with two hydrogens on the adjacent oxymethylene group, splitting into a triplet. δ 0.74 ppm represents the methylene hydrogen directly bonded to the silicon atom. In Figure 9, δ 8.67 ppm represents the four aromatic hydrogen atoms on the perylene ring skeleton. After the substituent is changed from bromine to a sterically hindered phenyl group, the benzene ring and the perylene ring plane twist due to steric hindrance. The perylene ring hydrogens are located in the deshielded region of the benzene ring, causing its chemical shift to significantly decrease from the original 8.18 ppm to 7.96 ppm, representing a group of aromatic hydrogens on the newly introduced four benzene rings. Hydrogen atoms, δ7.54~7.52ppm is the overlap peak of another group of aromatic hydrogen atoms on the benzene ring and the hydroxyl hydrogen on the boric acid group, δ3.95ppm is the 4 hydrogens on -N-CH2-, δ3.81ppm is the 12 hydrogens on the siloxane terminal group -O-CH2-CH3, δ1.79ppm is the 4 hydrogens on the intermediate bridging methylene group -CH2-CH2-CH2-, δ1.21ppm is the 18 hydrogens on the siloxane terminal group -O-CH2-CH3, and δ0.75ppm is the 4 hydrogens on the methylene group -CH2-Si near the silicon atom.

[0086] The final product prepared in Example 1 was sampled and subjected to mass spectrometry (the solvent was mass spectrometry grade methanol for dilution, the ion source was an electrospray ionization source, the scanning mode was positive ion mode, and the scanning range was 900-1500 Da). As shown in Figure 7, an extremely strong base peak appeared at m / z 1309.5. In positive ion mode, this indicates that the molecular ion of the compound absorbed a proton. Therefore, the precise molecular weight of the perylene-based modifier molecule can be confirmed as 1308.5 Da. This result is consistent with the theoretical molecular weight of complex perylene-based derivatives, indicating that the modifier has been successfully synthesized.

[0087] Based on Examples 1-4 and Comparative Examples 1-3, samples of the cured thermally conductive adhesive were taken for thermal conductivity testing: the cured thermally conductive adhesive was made into a circular sample with a diameter of 12.7 mm and a thickness of approximately 1 mm. A short laser pulse was applied to one side of the sample, and the temperature change curve of the back side over time was measured using an infrared detector. The thermal diffusivity was calculated, and then, combined with the specific heat capacity and bulk density, the thermal conductivity was calculated, referring to the standard GB / T 22588-2008 "Measurement of Thermal Diffusivity or Thermal Conductivity by Flash Method".

[0088] Based on Examples 1-4 and Comparative Examples 1-3, samples of the suspension prepared in step S31 were taken and viscosity was tested: referencing standard GB / T 2794-2022 "Determination of viscosity of adhesives".

[0089] The specific test results are shown in Table 2 and Figure 3: Table 2 Comparison of core performance of Examples 1-4 and Comparative Examples 1-3

[0090] The comparison results above show that Example 1 has the best overall performance. By modifying with a perylene modifier and adjusting the filler and magnetic field induction, it achieves high thermal conductivity, low viscosity and high shear strength. The thermal conductivity of Examples 2 to 4 is slightly lower than that of Example 1, but still remains at a high level. This indicates that excellent thermal conductivity was still achieved under a wide range of parameter variations. Comparative Example 1 did not use a perylene modifier, resulting in poor graphene dispersion, a significant decrease in thermal conductivity, an increase in viscosity and poor adhesion. Comparative Example 2 did not use spherical boron nitride and relied solely on magnetic modification of graphene, resulting in insufficient thermal conductivity. Although the adhesion was acceptable, the thermal conductivity was poor. Comparative Example 3 did not apply magnetic field induction, and the filler could not form an efficient thermal conduction path, resulting in low thermal conductivity.

[0091] In summary, it is clear from the above embodiments and comparative examples that the thermal adhesive for composite materials provided by the present invention is significantly superior to traditional solutions in terms of thermal conductivity. This is attributed to the modification of graphene, fillers, and magnetic field induction, thereby achieving improved thermal conductivity without sacrificing processability and adhesion.

Claims

1. A thermal adhesive for composite materials, comprising a matrix resin and a thermally conductive filler dispersed in the matrix, characterized in that: The matrix resin is a hyperbranched polymer containing terminal hydroxyl groups; the thermally conductive filler is a hybrid filler of modified graphene and spherical boron nitride microspheres; the modified graphene is modified with a perylene-based modifier and loaded with magnetic nanoparticles, the perylene-based modifier is non-covalently adsorbed onto the graphene surface through π-π bonds, and the quaternary ammonium salt cations it contains form positively charged sites on the graphene surface, hindering the aggregation of the graphene; the modified graphene is induced by an external magnetic field to form a through-type three-dimensional thermally conductive chain along the direction of the magnetic field lines, and the spherical boron nitride microspheres fill the gaps in the three-dimensional thermally conductive chain to form a three-dimensional composite structure.

2. The hot adhesive for composite materials according to claim 1, characterized in that: The thermally conductive filler comprises magnetically modified graphene accounting for 60-80% of the total filler content, and spherical boron nitride accounting for 20-40% of the total filler content.

3. The hot adhesive for composite materials according to claim 1, characterized in that: The magnetic nanoparticles are generated in situ from iron(III) oxide, prepared by ferric chloride and ferrous chloride under alkaline conditions in a molar ratio of 2:1, with the mass ratio of the two to the modified graphene being 5:

1.

4. A method for preparing the hot adhesive for composite materials according to any one of claims 1-3, characterized in that, Includes the following steps: S1: Preparation of modified graphene; S11: Graphene powder is added to N-methylpyrrolidone and ultrasonically treated in an ice-water bath to obtain a graphene suspension; S12: Perylene modifier is mixed with N-methylpyrrolidone and then added to the graphene suspension prepared in S11. The mixture is stirred, centrifuged, washed, dried, and ground to obtain modified graphene; S2: Magnetic modified graphene; S21: The modified graphene prepared in S12 is dissolved in deionized water and sodium dodecyl sulfate is added to obtain a modified suspension; S22: Mixed iron salts are added to the modified suspension prepared in S21, stirred, and the pH is adjusted to 10. The product is then collected by attracting with a magnet, washed, and dried to obtain magnetic modified graphene. S3: Preparation of thermal adhesive; S31: Dissolve hyperbranched polysiloxane resin in methyl ethyl ketone solvent, then add magnetically modified graphene and spherical boron nitride prepared in S22, stir to obtain a suspension; S32: Induce magnetic field induction and stir the suspension prepared in S31, degas under vacuum, then coat it on the surface of the composite material, heat and cure to obtain a cured thermally conductive adhesive.

5. The method for preparing a hot adhesive for composite materials according to claim 4, characterized in that: The ultrasonic treatment described in S11 has the following parameters: power 500-700W, on 2s / off 1s, duration 0.5-1.5h; the graphene suspension described in S11 has a concentration of 3-8mg / mL.

6. The method for preparing a hot adhesive for composite materials according to claim 4, characterized in that: The perylene modifier described in S12 has a mass ratio of 1:5 to 1:10 with graphene; the stirring described in S12 has the following parameters: temperature 50 to 70°C, rotation speed 400 to 600 rpm, and duration 3 to 5 hours.

7. The method for preparing a hot adhesive for composite materials according to claim 4, characterized in that: The centrifugation described in S12 has the following parameters: rotation speed 8000 rpm, duration 15 min; the drying described in S12 has the following parameters: temperature 60℃, duration 12 h.

8. The method for preparing a hot adhesive for composite materials according to claim 4, characterized in that: The sodium dodecyl sulfate described in S21 has a mass ratio of 1:10 to modified graphene.

9. The method for preparing a hot adhesive for composite materials according to claim 4, characterized in that: The stirring parameters described in S31 are: temperature 50-70℃, rotation speed 200-400rpm, and duration 20-40min; the suspension described in S31 has a hyperbranched polysiloxane resin solution concentration of 40-60%, and the total amount of filler added is 30-50% of the mass of the hyperbranched polysiloxane resin.

10. The method for preparing a hot adhesive for composite materials according to claim 4, characterized in that: The parameters for magnetic field induction described in S32 are: intensity 0.1–0.5T, duration 10–30 min; the parameters for stirring described in S32 are: rotation speed 50–150 rpm, duration 10–30 min; the parameters for vacuum degassing described in S32 are: temperature 40℃, vacuum degree -0.095 MPa, duration 20–40 min; and the parameters for temperature-curing described in S32 are: temperature 80–120℃, duration 1–3 h.

Images