An epoxy resin / boron nitride nanosheet composite and a preparation method thereof

Abstract

The application belongs to the technical field of composite materials, and discloses an epoxy resin / boron nitride nanosheet composite material and a preparation method thereof. The composite material comprises an epoxy resin matrix and boron nitride nanosheets modified with a flame retardant and dispersed in the epoxy resin matrix. The flame retardant on the surface of the boron nitride nanosheets modified with the flame retardant is adsorbed on the surface of the boron nitride nanosheets through physical action, and the flame retardant is a phosphorus-containing organic compound with a benzene ring. The flame retardant is modified on the surface of the boron nitride nanosheets through physical action, the interface compatibility of the boron nitride and the epoxy resin matrix is improved, the dispersibility of the boron nitride is improved, and the thermal conductivity of the composite material is improved. Meanwhile, the physical barrier effect of the boron nitride nanosheets and the catalytic carbonization effect of the flame retardant enable the composite material to have excellent flame retardancy. The application can effectively solve the technical problems of poor dispersibility of boron nitride in the epoxy resin matrix, poor thermal conductivity and poor flame retardancy of the epoxy resin.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, and more specifically, relates to an epoxy resin / boron nitride nanosheet composite material and its preparation method. Background Technology

[0002] With the advent of the 5G era, the computing speed of computers and other electronic devices is increasing rapidly, and electronic components are becoming more highly integrated and miniaturized. This has led to a sharp increase in the heat power density of electronic devices, resulting in a significant rise in thermal failure and fire hazards. Therefore, thermal interface materials with both high thermal conductivity and high flame retardancy are crucial for extending the lifespan of electronic devices and ensuring their stable and reliable operation. Epoxy resin, due to its advantages such as light weight, low cost, good processability, electrical insulation, and corrosion resistance, is currently the preferred encapsulation material in the electronic packaging field. However, epoxy resin has a relatively low intrinsic thermal conductivity. Furthermore, compared to ceramic encapsulation materials, epoxy resin is flammable, affecting the safe operation of electronic devices and posing a significant threat to people's lives and property.

[0003] Currently, incorporating two-dimensional inorganic materials (such as boron nitride and graphene) as high-performance additives into epoxy resin matrices is a common strategy to simultaneously improve the thermal conductivity and flame retardancy of epoxy resins. This is achieved by using the thermally conductive pathways formed by the two-dimensional inorganic materials to promote phonon transfer and by creating physical barriers to block oxygen and heat exchange during combustion. Although the barrier effect of two-dimensional materials can improve the flame retardancy of epoxy resins to some extent, the effect is often unsatisfactory. Therefore, in existing technologies, to improve the thermal conductivity and flame retardancy of epoxy resins, it is usually necessary to simultaneously add fillers with high thermal conductivity and additives with flame retardant functions. To address the poor interfacial interaction between the thermally conductive fillers and flame retardant additives and the epoxy resin matrix, it is often necessary to chemically or physically modify the thermally conductive fillers and flame retardant additives separately, resulting in complex and time-consuming processes that are not conducive to practical applications.

[0004] Hexagonal boron nitride (h-BN) with a graphene-like two-dimensional structure is advantageous due to its high aspect ratio, low dielectric constant (~34.8), and high thermal conductivity (~800 W / m²). -1 K -1 It has good thermal stability and a low coefficient of thermal expansion (2×10). -6 k -1 The advantages of h-BN, such as its ability to form a composite material, have been widely studied and noted. However, the poor interfacial compatibility between h-BN and the epoxy resin matrix leads to significant thermal resistance at the filler-matrix interface, limiting the improvement of the composite material's thermal conductivity. Furthermore, achieving the desired thermal conductivity often requires increasing the amount of h-BN added, which can easily cause h-BN agglomeration, severely impairing the composite material's mechanical properties and limiting the barrier effect of the two-dimensional sheet structure on improving the flame retardant properties of the composite material.

[0005] Therefore, if a convenient preparation method can be developed to obtain epoxy resin-based materials that combine thermal conductivity and flame retardancy, the above problems can be effectively solved. Summary of the Invention

[0006] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide an epoxy resin / boron nitride nanosheet composite material and its preparation method. The method utilizes mechanical processing (such as one-step ball milling) to physically modify the surface of boron nitride nanosheets with a flame retardant. This flame-retardant-modified boron nitride nanosheet is then added as a filler to epoxy resin. The surface-modified flame retardant imparts a strong interfacial interaction between the boron nitride nanosheets and the epoxy resin, improving the interfacial compatibility between boron nitride and the epoxy resin matrix, promoting the uniform distribution of boron nitride nanosheets, reducing interfacial thermal resistance, and establishing thermal conductivity pathways, thereby improving the thermal conductivity of the composite material. Simultaneously, the physical barrier effect of the boron nitride nanosheets and the catalytic carbonization effect of the flame retardant endow the composite material with excellent flame retardancy. This invention effectively solves the technical problems of poor dispersibility of boron nitride in the epoxy resin matrix and poor thermal conductivity and flame retardancy of the epoxy resin.

[0007] To achieve the above objectives, according to one aspect of the present invention, an epoxy resin / boron nitride nanosheet composite material is provided, characterized in that it comprises an epoxy resin matrix and boron nitride nanosheets modified with a flame retardant dispersed in the epoxy resin matrix; wherein the mass ratio of the epoxy resin matrix to the boron nitride nanosheets modified with the flame retardant is 60:40 to 95:5; the flame retardant on the surface of the boron nitride nanosheets modified with the flame retardant is adsorbed onto the surface of the boron nitride nanosheets by physical action, and the flame retardant is a phosphorus-containing organic compound having a benzene ring.

[0008] As a further preferred embodiment of the present invention, the flame retardant is one or more of phenylphosphonic acid, phenylphosphonous acid, diethyl phenylphosphonate, and diphenylphosphonic acid.

[0009] As a further preferred embodiment of the present invention, the epoxy resin matrix is ​​bisphenol A type epoxy resin, bisphenol F type epoxy resin, or liquid crystal epoxy resin.

[0010] According to another aspect of the present invention, the present invention provides a method for preparing the above-mentioned epoxy resin / boron nitride nanosheet composite material, characterized in that it includes the following steps:

[0011] (1) Place hexagonal boron nitride, flame retardant and grinding balls in a ball milling jar and perform dry ball milling;

[0012] (2) The ball milling product obtained in step (1) is dispersed in a solvent and washed with the solvent to remove the free flame retardant, thereby obtaining flame-retardant functionalized boron nitride nanosheets.

[0013] (3) Disperse the flame-retardant functionalized boron nitride nanosheets obtained in step (2) into a solvent to obtain a dispersion of flame-retardant functionalized boron nitride nanosheets.

[0014] (4) Dissolve the epoxy resin in a solvent, then mix it thoroughly with the dispersion of flame-retardant functionalized boron nitride nanosheets, and then remove the solvent to obtain a mixture of flame-retardant functionalized boron nitride nanosheets and epoxy resin.

[0015] (5) Add the curing agent to the mixture obtained in step (4), mix evenly and degas, and after curing reaction, epoxy resin / boron nitride nanosheet composite material can be obtained.

[0016] As a further preferred embodiment of the present invention, in step (1), the particle size of the hexagonal boron nitride is 1 μm to 10 μm; the flame retardant is one or more of phenylphosphonic acid, phenylphosphonous acid, diethyl phenylphosphonate, and diphenylphosphonic acid; the mass ratio of the hexagonal boron nitride to the flame retardant is 1:1 to 1:60; and the grinding balls are selected from agate grinding balls or zirconium oxide grinding balls with a diameter of 2 to 10 mm.

[0017] As a further preferred embodiment of the present invention, in steps (2) and (3), the dispersion is specifically carried out by one or more of ultrasonic treatment, magnetic stirring, and mechanical stirring.

[0018] As a further preferred embodiment of the present invention, in step (2), the solvent is one or more of deionized water, ethanol, dichloromethane, and acetone;

[0019] In steps (3) and (4), the solvent is a solvent capable of dissolving the epoxy resin precursor, preferably one or more of dichloromethane, acetone, chloroform, N,N-dimethylformamide, and ethyl acetate.

[0020] As a further preferred embodiment of the present invention, in step (4), the solvent removal is specifically carried out by one or more of the following methods: vacuum distillation, vacuum drying, and heat drying.

[0021] As a further preferred embodiment of the present invention, the curing agent includes imidazole curing agents, amine curing agents, or acid anhydride curing agents.

[0022] Compared with the prior art, the technical solution conceived in this invention uses a phosphorus-containing organic compound with a benzene ring as a flame retardant. The flame retardant is adsorbed onto the surface of boron nitride nanosheets through physical action, resulting in flame retardant-modified boron nitride nanosheets (for example, flame retardant-assisted mechanical ball milling can be used to exfoliate hexagonal boron nitride to obtain flame retardant-modified boron nitride nanosheets, in which case the surface of the boron nitride nanosheets contains flame retardants adsorbed through π-π interactions or electrostatic interactions). Using the flame retardant-modified boron nitride nanosheets as a functional filler for epoxy resin can improve the interfacial compatibility between boron nitride nanosheets and the epoxy resin matrix, and promote the uniform dispersion of boron nitride nanosheets in the epoxy resin matrix. The resulting epoxy resin boron nitride nanosheet composite material has good flame retardant and thermal conductivity properties, as well as good mechanical properties, effectively solving the problems of poor dispersion of boron nitride nanosheets in epoxy resin, low thermal conductivity of epoxy resin, and flammability.

[0023] Compared to existing technologies, the composite material of this invention has significant advantages in performance and preparation. The surface inertness of hexagonal boron nitride leads to poor interfacial compatibility with the polymer matrix, resulting in high thermal resistance at the filler-matrix interface, affecting the thermal conductivity of the composite material. Furthermore, filler aggregation can create stress concentration points, reducing the mechanical properties of the composite material. Generally, chemical modification of hexagonal boron nitride is the preferred approach to solve key problems such as poor interfacial compatibility between hexagonal boron nitride and polymers, and poor dispersibility in the polymer matrix. Currently, commonly used modifiers for boron nitride surface modification include sodium hydroxide, urea, and polydopamine. Modified boron nitride nanosheets exhibit good dispersibility in polymers, but the effect of boron nitride alone on improving the flame retardant properties of epoxy resin matrices is limited. Therefore, in addition to modifying the active groups, further improving the interfacial compatibility between boron nitride and epoxy resin while enhancing the flame retardant properties of the composite material would be more beneficial for its application. However, separately improving the filler dispersibility and the overall flame retardancy of the composite material (in existing technologies, flame retardant functional additives are often added to the resin material to improve flame retardancy) inevitably leads to cumbersome steps, high costs, long processing times, and complex processes, which are not conducive to large-scale practical production and application. Therefore, this invention provides a simple one-step process to modify the surface of boron nitride nanosheets with a physically adsorbed flame retardant. For example, a flame retardant-assisted ball milling exfoliation method can be used. Under mechanical force, hexagonal boron nitride is exfoliated into few-layer boron nitride nanosheets, and the flame retardant adheres to the surface of the boron nitride nanosheets through π-π interactions or electrostatic interactions, resulting in flame retardant-functionalized boron nitride nanosheets. This method is simple to operate and can be mass-produced. The flame retardant modified on the boron nitride surface and the epoxy resin have hydrogen bond interactions, which not only promote the uniform dispersion of the boron nitride nanosheets and ensure the mechanical properties of the composite material, but also reduce the interfacial thermal resistance between boron nitride and epoxy resin, improving thermal conductivity. On the other hand, flame retardant-functionalized boron nitride nanosheets can improve the flame retardant properties of materials.

[0024] Specifically, the present invention can achieve the following beneficial effects:

[0025] (1) The epoxy resin boron nitride nanosheet composite material of the present invention has a few-layer structure due to the flame retardant-modified boron nitride nanosheets, which increases the specific surface area of ​​boron nitride and thus realizes the overlap of the thermal conductivity pathways of boron nitride nanosheets. Furthermore, by adjusting the mass ratio of filler to epoxy resin, the material can have different thermal conductivity, mechanical strength and other physicochemical properties to meet different practical application requirements.

[0026] (2) The epoxy resin boron nitride nanosheet composite material of the present invention improves the flame retardancy of the material by forming a physical barrier to block combustible gases and heat exchange. At the same time, since the surface of the provided boron nitride nanosheets is modified with flame retardant, the flame retardant performance can be further improved.

[0027] (3) The epoxy resin boron nitride nanosheet composite material provided by the present invention has a flame retardant modified on the surface of the boron nitride nanosheet, which realizes the uniform dispersion of boron nitride nanosheet and the overlap of thermal conduction pathways, reduces the interfacial thermal resistance, and improves the thermal conductivity of the epoxy resin composite material.

[0028] (4) The epoxy resin boron nitride nanosheet composite material provided by the present invention has flame retardant modified on the surface of boron nitride. The flame retardant and epoxy resin have interfacial interaction, which improves the interfacial compatibility between the filler and the epoxy resin matrix and improves the mechanical strength and mechanical properties of epoxy resin.

[0029] (5) The method for preparing the flame retardant-modified boron nitride nanosheets provided by the present invention performs flame retardant functionalization on the boron nitride nanosheets while exfoliating them. The preparation method is simple, mild, green and environmentally friendly, and suitable for large-scale production.

[0030] (6) The epoxy resin boron nitride nanosheet composite material of the present invention has excellent thermal conductivity, flame retardancy and mechanical properties. As a thermal interface material, it can be applied in the field of electronic packaging, such as between chips and micro heat sinks, to improve the heat transfer efficiency between chips and heat sinks, reduce the interface thermal resistance between chips and micro heat sinks, ensure that chips operate at safe temperatures, and extend the service life of electronic devices.

[0031] This invention, in particular, utilizes a one-step ball milling method assisted by a flame retardant to exfoliate hexagonal boron nitride into boron nitride nanosheets. Simultaneously, the flame retardant is physically adsorbed onto the surface of the boron nitride nanosheets. This physical modification with the flame retardant does not hinder the connectivity of the thermally conductive network within the boron nitride nanosheets, ensuring that the intrinsic thermal conductivity of boron nitride remains unaffected. The flame retardant modification not only effectively solves the technical problem of poor dispersibility of boron nitride in epoxy resin matrices but also addresses the flammability issue of epoxy resins. Adding flame-retardant-modified boron nitride nanosheets to epoxy resin results in a composite material exhibiting excellent thermal conductivity and flame retardancy, along with good mechanical properties, due to the good dispersibility and interfacial interactions of the flame-retardant functionalized boron nitride. The method in this invention is simple, easy to implement, and can be mass-produced, possessing high practical application value.

[0032] In summary, this invention can effectively solve the technical problem of poor dispersibility of boron nitride in epoxy resin matrix, and improve the thermal conductivity and flame retardant properties of epoxy resin. Attached Figure Description

[0033] Figure 1 This is a transmission electron microscope image of boron nitride nanosheets modified with phenylphosphonic acid.

[0034] Figure 2 These are elemental energy distribution images of phenylphosphonic acid-modified boron nitride nanosheets.

[0035] Figure 3 This is a scanning electron microscope image of the packing dispersion effect in Example 1.

[0036] Figure 4 This is a scanning electron microscope image of the dispersion effect of hexagonal boron nitride in Comparative Example 2.

[0037] Figure 5 This is a scanning electron microscope image of the packing dispersion effect in Example 2.

[0038] Figure 6 These are comparative graphs showing the thermal conductivity tests of Examples 1-4 and Comparative Examples 1-5.

[0039] Figure 7 These are comparison diagrams of bending tests for Example 1 and Comparative Examples 1 and 2.

[0040] Figure 8 This is a comparison chart of the bonding test results of steel sheets in Example 1 and Comparative Examples 1 and 2. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0042] The epoxy resin / boron nitride nanosheet composite material of the present invention is an epoxy resin flame-retardant functionalized boron nitride nanosheet composite material, comprising an epoxy resin matrix and flame-retardant functionalized boron nitride nanosheets (i.e. flame-retardant modified hexagonal boron nitride nanosheets) filled in the epoxy resin matrix.

[0043] The epoxy resin matrix material in this invention is commercially available. In some embodiments, the epoxy resin is bisphenol A type epoxy resin, bisphenol F type epoxy resin, or liquid crystal epoxy resin, or it can be a self-made epoxy resin.

[0044] In some embodiments, at least a portion of the flame retardant is adsorbed onto the surface of the flame retardant-modified boron nitride nanosheets through π-π interactions or electrostatic interactions.

[0045] In some embodiments, the content of flame retardant-modified hexagonal boron nitride nanosheets in the composite material is 5 wt% to 40 wt%, preferably 5 wt% to 30 wt%, and particularly preferably 5 wt% to 20 wt%.

[0046] In some embodiments, the epoxy resin / boron nitride nanosheet composite material can be prepared according to the following method:

[0047] (1) Place hexagonal boron nitride, flame retardant, and grinding balls in a ball mill jar and perform ball milling;

[0048] (2) Collect the product from ball milling in step (1), disperse it in a solvent and wash it with the solvent to remove the free flame retardant, and obtain flame-retardant functionalized boron nitride nanosheets.

[0049] (3) Disperse the flame-retardant functionalized boron nitride nanosheets obtained in step (2) into a solvent to obtain a dispersion of flame-retardant functionalized boron nitride nanosheets.

[0050] (4) Dissolve the epoxy resin in a solvent, then mix it thoroughly with the dispersion of flame-retardant functionalized boron nitride nanosheets, and then remove the solvent to obtain a mixture of flame-retardant functionalized boron nitride nanosheets and epoxy resin.

[0051] (5) Add the curing agent to the mixture obtained in step (4), mix evenly and degas, and after curing reaction, thermally conductive and flame-retardant epoxy resin boron nitride nanosheet composite material can be obtained.

[0052] In some embodiments, the mass ratio of hexagonal boron nitride to flame retardant in step (1) is 1:1 to 1:60; the particle size of the hexagonal boron nitride is 1 μm to 10 μm; the grinding ball is an agate grinding ball or a zirconium oxide grinding ball with a diameter of 2 to 10 mm; the flame retardant is a phosphorus-containing organic compound with a benzene ring. In preferred embodiments, the flame retardant is any one of phenylphosphonic acid, phenylphosphonous acid, diphenylphosphonic acid, and diethyl phenylphosphonate.

[0053] In some embodiments, the solvent in step (2) is one or more of deionized water, ethanol, dichloromethane, and acetone.

[0054] In some embodiments, the solvents in steps (3) and (4) are one or more of dichloromethane, acetone, chloroform, N,N-dimethylformamide, and ethyl acetate.

[0055] In some embodiments, the curing agent described in step (5) includes imidazole curing agents, amine curing agents, or acid anhydride curing agents.

[0056] In some embodiments, the solvent removal method includes physical methods such as heating and drying, vacuum drying, and reduced pressure distillation. The dispersion method includes methods such as magnetic stirring, mechanical stirring, and ultrasonic treatment.

[0057] The following are specific examples:

[0058] Example 1

[0059] An epoxy resin boron nitride nanosheet composite material. This epoxy resin boron nitride nanosheet composite material includes an epoxy resin matrix and flame-retardant functionalized boron nitride nanosheets filled in the epoxy resin matrix. Hexagonal boron nitride is exfoliated into few-layer boron nitride nanosheets using a flame-retardant-assisted ball milling exfoliation method. Simultaneously, the flame retardant is adsorbed onto the surface of the boron nitride nanosheets through π-π interactions or electrostatic interactions. The resulting flame-retardant functionalized boron nitride nanosheets are then filled into the epoxy resin matrix as a thermally conductive and flame-retardant filler. The flame retardant is phenylphosphonic acid; the epoxy resin is bisphenol F type epoxy resin; and the flame-retardant-modified boron nitride nanosheets in the epoxy resin matrix account for 5% of the total mass of the composite material.

[0060] The preparation method of the epoxy resin boron nitride nanosheet composite material includes the following steps:

[0061] (1) Place 1.0g of hexagonal boron nitride with a horizontal dimension of about 10μm, 20g of phenylphosphonic acid, 50g of agate grinding balls with a diameter of 10mm and 90g of agate grinding balls with a diameter of 2-4mm in a polytetrafluoroethylene grinding jar, fix the grinding jar in a planetary ball mill, and grind at a speed of 300rpm for 20 hours.

[0062] (2) The ball milling product obtained in step (1) is dispersed in water, sonicated for 1 hour, and washed with water, ethanol and acetone in sequence and filtered to remove free flame retardant, so as to obtain flame-retardant functionalized boron nitride nanosheets.

[0063] (3) Disperse the flame-retardant functionalized boron nitride nanosheets obtained in step (2) into acetone, sonicate for 1 hour, stir for 1 hour, and obtain a dispersion of flame-retardant functionalized boron nitride nanosheets with a concentration of 14 mg / g.

[0064] (4) Dissolve 20g of epoxy resin in acetone and mix it with 79.7g of flame-retardant functionalized boron nitride nanosheet dispersion. Stir for 1h, sonicate for 1h, then distill under reduced pressure at 60℃ for at least 30 minutes to remove most of the solvent, and then place it in a vacuum oven at 60℃ overnight to obtain a mixture of flame-retardant functionalized boron nitride nanosheet and epoxy resin.

[0065] (5) 1.2g of curing agent 2-ethyl-4-methylimidazole was added to the mixture obtained in step (4). The mass ratio of 2-ethyl-4-methylimidazole to epoxy resin was 6:100. The mixture was thoroughly mixed and degassed, then cast into a polytetrafluoroethylene mold and placed in an oven for curing. The curing conditions were 60℃ for 2 hours and 150℃ for 8 hours to obtain a thermally conductive and flame-retardant epoxy resin boron nitride nanosheet composite material with a filler content of 5wt%.

[0066] Example 2

[0067] An epoxy resin boron nitride nanosheet composite material. This epoxy resin boron nitride nanosheet composite material includes an epoxy resin matrix and flame-retardant functionalized boron nitride nanosheets filled in the epoxy resin matrix. Hexagonal boron nitride is exfoliated into few-layer boron nitride nanosheets using a flame-retardant-assisted ball milling exfoliation method. Simultaneously, the flame retardant is adsorbed onto the surface of the boron nitride nanosheets through π-π interactions or electrostatic interactions. The resulting flame-retardant functionalized boron nitride nanosheets are then filled into the epoxy resin matrix as a thermally conductive and flame-retardant filler. The flame retardant is phenylphosphonic acid; the epoxy resin is bisphenol F type epoxy resin; and the flame-retardant-modified boron nitride nanosheets in the epoxy resin matrix account for 10% of the total mass of the composite material.

[0068] The preparation method of the epoxy resin boron nitride nanosheet composite material includes the following steps:

[0069] (1) Place 1.0g of hexagonal boron nitride with a horizontal dimension of about 10μm, 20g of phenylphosphonic acid, 50g of agate grinding balls with a diameter of 10mm and 90g of agate grinding balls with a diameter of 2-4mm in a polytetrafluoroethylene grinding jar, fix the grinding jar in a planetary ball mill, and grind at a speed of 300rpm for 20 hours.

[0070] (2) The ball milling product obtained in step (1) is dispersed in water, sonicated for 1 hour, and washed with water, ethanol and acetone in sequence and filtered to remove free flame retardant, so as to obtain flame-retardant functionalized boron nitride nanosheets.

[0071] (3) Disperse the flame-retardant functionalized boron nitride nanosheets obtained in step (2) into acetone, sonicate for 1 hour, stir for 1 hour, and obtain a dispersion of flame-retardant functionalized boron nitride nanosheets with a concentration of 14 mg / g.

[0072] (4) Dissolve 20g of epoxy resin in acetone and mix it with 168.3g of flame-retardant functionalized boron nitride nanosheet dispersion. Stir for 1h, sonicate for 1h, then distill under reduced pressure at 60℃ for at least 30 minutes to remove most of the solvent, and then place it in a vacuum oven at 60℃ overnight to obtain a mixture of flame-retardant functionalized boron nitride nanosheets and epoxy resin.

[0073] (5) 1.2g of curing agent 2-ethyl-4-methylimidazole was added to the mixture obtained in step (4). The mass ratio of 2-ethyl-4-methylimidazole to epoxy resin was 6:100. The mixture was thoroughly mixed and degassed, then cast into a polytetrafluoroethylene mold and placed in an oven for curing. The curing conditions were 60℃ for 2 hours and 150℃ for 8 hours to obtain a thermally conductive and flame-retardant epoxy resin boron nitride nanosheet composite material with a filler content of 10wt%.

[0074] Example 3

[0075] An epoxy resin boron nitride nanosheet composite material. This epoxy resin boron nitride nanosheet composite material includes an epoxy resin matrix and flame-retardant functionalized boron nitride nanosheets filled in the epoxy resin matrix. Hexagonal boron nitride is exfoliated into few-layer boron nitride nanosheets using a flame-retardant-assisted ball milling exfoliation method. Simultaneously, the flame retardant is adsorbed onto the surface of the boron nitride nanosheets through π-π interactions or electrostatic interactions. The resulting flame-retardant functionalized boron nitride nanosheets are then filled into the epoxy resin matrix as a thermally conductive and flame-retardant filler. The flame retardant is phenylphosphonic acid; the epoxy resin is bisphenol F type epoxy resin; and the flame-retardant-modified boron nitride nanosheets in the epoxy resin matrix account for 20% of the total mass of the composite material.

[0076] The preparation method of the epoxy resin boron nitride nanosheet composite material includes the following steps:

[0077] (1) Place 1.0g of hexagonal boron nitride with a horizontal dimension of about 10μm, 20g of phenylphosphonic acid, 50g of agate grinding balls with a diameter of 10mm and 90g of agate grinding balls with a diameter of 2-4mm in a polytetrafluoroethylene grinding jar, fix the grinding jar in a planetary ball mill, and grind at a speed of 300rpm for 20 hours.

[0078] (2) The ball milling product obtained in step (1) is dispersed in water, sonicated for 1 hour, and washed with water, ethanol and acetone in sequence and filtered to remove free flame retardant, so as to obtain flame-retardant functionalized boron nitride nanosheets.

[0079] (3) Disperse the flame-retardant functionalized boron nitride nanosheets obtained in step (2) into acetone, sonicate for 1 hour, stir for 1 hour, and obtain a dispersion of flame-retardant functionalized boron nitride nanosheets with a concentration of 14 mg / g.

[0080] (4) Dissolve 20g of epoxy resin in acetone and mix it with 378.6g of flame-retardant functionalized boron nitride nanosheet dispersion. Stir for 1h, sonicate for 1h, then distill under reduced pressure at 60℃ for at least 30 minutes to remove most of the solvent, and then place it in a vacuum oven at 60℃ overnight to obtain a mixture of flame-retardant functionalized boron nitride nanosheets and epoxy resin.

[0081] (5) Add 1.2g of curing agent 2-ethyl-4-methylimidazole to the mixture obtained in step (4). The mass ratio of 2-ethyl-4-methylimidazole to epoxy resin is 6:100. Mix evenly and degas. Then add the mixture to a stainless steel mold and pre-cur it by hot pressing for 2h at 60℃ and 2MPa pressure using a flat vulcanizing machine. Then place it in an oven and treat it at 150℃ for 8h to obtain a thermally conductive and flame-retardant epoxy resin boron nitride nanosheet composite material with a filler content of 20wt%.

[0082] Example 4

[0083] An epoxy resin boron nitride nanosheet composite material. This epoxy resin boron nitride nanosheet composite material includes an epoxy resin matrix and flame-retardant functionalized boron nitride nanosheets filled in the epoxy resin matrix. Hexagonal boron nitride is exfoliated into few-layer boron nitride nanosheets using a flame-retardant-assisted ball milling exfoliation method. Simultaneously, the flame retardant is adsorbed onto the surface of the boron nitride nanosheets through π-π interactions or electrostatic interactions. The resulting flame-retardant functionalized boron nitride nanosheets are then filled into the epoxy resin matrix as a thermally conductive and flame-retardant filler. The flame retardant is phenylphosphonic acid; the epoxy resin is bisphenol F type epoxy resin; and the flame-retardant-modified boron nitride nanosheets in the epoxy resin matrix account for 30% of the total mass of the composite material.

[0084] The preparation method of the epoxy resin boron nitride nanosheet composite material includes the following steps:

[0085] (1) Place 1.0g of hexagonal boron nitride with a horizontal dimension of about 10μm, 20g of phenylphosphonic acid, 50g of agate grinding balls with a diameter of 10mm and 90g of agate grinding balls with a diameter of 2-4mm in a polytetrafluoroethylene grinding jar, fix the grinding jar in a planetary ball mill, and grind at a speed of 300rpm for 20 hours.

[0086] (2) The ball milling product obtained in step (1) is dispersed in water, sonicated for 1 hour, and washed with water, ethanol and acetone in sequence and filtered to remove free flame retardant, so as to obtain flame-retardant functionalized boron nitride nanosheets.

[0087] (3) Disperse the flame-retardant functionalized boron nitride nanosheets obtained in step (2) into acetone, sonicate for 1 hour, stir for 1 hour, and obtain a dispersion of flame-retardant functionalized boron nitride nanosheets with a concentration of 14 mg / g.

[0088] (4) Dissolve 20g of epoxy resin in acetone and mix it with 649g of flame-retardant functionalized boron nitride nanosheet dispersion. Stir for 1h, sonicate for 1h, then distill under reduced pressure at 60℃ for at least 30 minutes to remove most of the solvent, and then place it in a vacuum oven at 60℃ overnight to obtain a mixture of flame-retardant functionalized boron nitride nanosheets and epoxy resin.

[0089] (5) Add 1.2g of curing agent 2-ethyl-4-methylimidazole to the mixture obtained in step (4). The mass ratio of 2-ethyl-4-methylimidazole to epoxy resin is 6:100. Mix evenly and degas. Then add the mixture to a stainless steel mold and pre-cur it by hot pressing for 2h at 60℃ and 2MPa pressure using a flat vulcanizing machine. Then place it in an oven and treat it at 150℃ for 8h to obtain a thermally conductive and flame-retardant epoxy resin boron nitride nanosheet composite material with a filler content of 30wt%.

[0090] Example 5

[0091] An epoxy resin boron nitride nanosheet composite material. This epoxy resin boron nitride nanosheet composite material includes an epoxy resin matrix and flame-retardant functionalized boron nitride nanosheets filled in the epoxy resin matrix. Hexagonal boron nitride is exfoliated into few-layer boron nitride nanosheets using a flame-retardant-assisted ball milling exfoliation method. Simultaneously, the flame retardant is adsorbed onto the surface of the boron nitride nanosheets through π-π interactions or electrostatic interactions. The resulting flame-retardant functionalized boron nitride nanosheets are then filled into the epoxy resin matrix as a thermally conductive and flame-retardant filler. The flame retardant is diphenylphosphonic acid; the epoxy resin is a bisphenol A type epoxy resin; and the flame-retardant-modified boron nitride nanosheets in the epoxy resin matrix account for 40% of the total mass of the composite material.

[0092] The preparation method of the epoxy resin boron nitride nanosheet composite material includes the following steps:

[0093] (1) Place 1g of hexagonal boron nitride with a horizontal dimension of about 1μm, 50g of diphenylphosphonic acid, 50g of agate grinding balls with a diameter of 10mm and 90g of agate grinding balls with a diameter of 2-4mm in a polytetrafluoroethylene grinding jar, fix the grinding jar in a planetary ball mill, and grind at a speed of 300rpm for 20 hours.

[0094] (2) The ball milling product obtained in step (1) is dispersed in water, sonicated for 1 hour, and washed with water and dichloromethane in sequence and filtered to remove free flame retardant, so as to obtain flame retardant functionalized boron nitride nanosheets.

[0095] (3) Disperse the flame-retardant functionalized boron nitride nanosheets obtained in step (2) into dichloromethane, sonicate for 1 hour, stir for 1 hour, and obtain a dispersion of flame-retardant functionalized boron nitride nanosheets with a concentration of 14 mg / g.

[0096] (4) Dissolve 14g of epoxy resin in dichloromethane and mix it with 952.4g of flame-retardant functionalized boron nitride nanosheet dispersion. Stir for 1h, sonicate for 1h, then distill under reduced pressure at 60℃ for at least 30 minutes to remove most of the solvent, and then place it in a vacuum oven at 60℃ overnight to obtain a mixture of flame-retardant functionalized boron nitride nanosheets and epoxy resin.

[0097] (5) Add 6g of curing agent 4,4-diaminodiphenylmethane to the mixture obtained in step (4). The mass ratio of 4,4-diaminodiphenylmethane to epoxy resin is 30:70. Mix evenly and degas. Then add the mixture to a stainless steel mold and heat-press it for 2 hours at 100°C and 2MPa pressure using a flat vulcanizing machine. Then place it in an oven and cure it at 160°C for 4 hours to obtain a thermally conductive and flame-retardant epoxy resin boron nitride nanosheet composite material with a filler content of 40wt%.

[0098] Example 6

[0099] An epoxy resin boron nitride nanosheet composite material. This epoxy resin boron nitride nanosheet composite material includes an epoxy resin matrix and flame-retardant functionalized boron nitride nanosheets filled in the epoxy resin matrix. Hexagonal boron nitride is exfoliated into few-layer boron nitride nanosheets using a flame-retardant-assisted ball milling exfoliation method. Simultaneously, the flame retardant is adsorbed onto the surface of the boron nitride nanosheets through π-π interactions or electrostatic interactions. The resulting flame-retardant functionalized boron nitride nanosheets are then used as thermally conductive and flame-retardant fillers in the epoxy resin matrix. The flame retardant is diethyl phenylphosphonate; the epoxy resin is a liquid crystal epoxy resin; and the flame-retardant-modified boron nitride nanosheets in the epoxy resin matrix account for 10% of the total mass of the composite material.

[0100] The preparation method of the epoxy resin boron nitride nanosheet composite material includes the following steps:

[0101] (1) Place 1g of hexagonal boron nitride with a horizontal dimension of about 10μm, 1g of diethyl phenylphosphonate, 50g of zirconium oxide grinding balls with a diameter of 10mm and 90g of zirconium oxide grinding balls with a diameter of 2-4mm in a polytetrafluoroethylene grinding jar, fix the grinding jar in a planetary ball mill, and grind at a speed of 300rpm for 20 hours.

[0102] (2) The ball-milled product obtained in step (1) is dispersed in dichloromethane, sonicated for 1 hour, and washed and filtered with dichloromethane to remove free flame retardant, thereby obtaining flame-retardant functionalized boron nitride nanosheets.

[0103] (3) Disperse the flame-retardant functionalized boron nitride nanosheets obtained in step (2) into chloroform, sonicate for 1 hour, stir for 1 hour, and obtain a dispersion of flame-retardant functionalized boron nitride nanosheets with a concentration of 14 mg / g.

[0104] (4) Dissolve 6.9g of liquid crystal epoxy resin monomer 4,4'-biphenyl bisphenol diglycidyl ether in chloroform and mix it with 71.4g of flame-retardant functionalized boron nitride nanosheet dispersion. Stir for 1h, sonicate for 1h, then distill under reduced pressure at 60℃ for at least 30 minutes to remove most of the solvent, and then place it in a vacuum oven at 60℃ overnight to obtain a mixture of flame-retardant functionalized boron nitride nanosheets and epoxy resin.

[0105] (5) Add 2.1g of curing agent 4,4-diaminodiphenylmethane to the mixture obtained in step (4), mix evenly, then add the mixture to a stainless steel mold, and hot-press and cure for 2h at 100℃ and 2MPa pressure using a flat vulcanizing machine. Then place it in an oven and cure at 160℃ for 4h to obtain a thermally conductive and flame-retardant epoxy resin boron nitride nanosheet composite material with a filler content of 10wt%.

[0106] Example 7

[0107] A boron nitride nanosheet epoxy resin composite material. This composite material comprises an epoxy resin matrix and flame-retardant-functionalized boron nitride nanosheets filled within the epoxy resin matrix. Hexagonal boron nitride is exfoliated into few-layer boron nitride nanosheets using a flame-retardant-assisted ball milling method. Simultaneously, the flame retardant is adsorbed onto the surface of the boron nitride nanosheets through π-π interactions or electrostatic interactions. The resulting flame-retardant-functionalized boron nitride nanosheets are then used as thermally conductive and flame-retardant fillers in the epoxy resin matrix. The flame retardant is phenylphosphonic acid; the epoxy resin is a liquid crystal epoxy resin; and the flame-retardant-modified boron nitride nanosheets in the epoxy resin matrix account for 10% of the total mass of the composite material.

[0108] The preparation method of the epoxy resin boron nitride nanosheet composite material includes the following steps:

[0109] (1) Place 1g of hexagonal boron nitride with a horizontal dimension of about 10μm, 60g of phenylphosphine acid, 50g of zirconium oxide grinding balls with a diameter of 10mm and 90g of zirconium oxide grinding balls with a diameter of 2-4mm in a polytetrafluoroethylene grinding jar, fix the grinding jar in a planetary ball mill, and grind at a speed of 300rpm for 20 hours.

[0110] (2) The ball milling product obtained in step (1) is dispersed in dichloromethane, sonicated for 0.5 h, stirred for 0.5 h, and washed and filtered with dichloromethane to remove free flame retardant, so as to obtain flame-retardant functionalized boron nitride nanosheets.

[0111] (3) Disperse the flame-retardant functionalized boron nitride nanosheets obtained in step (2) into N,N-dimethylformamide, sonicate for 1 h, stir for 1 h, and obtain a dispersion of flame-retardant functionalized boron nitride nanosheets with a concentration of 14 mg / g.

[0112] (4) Dissolve 6.9g of liquid crystal epoxy resin monomer 4,4'-biphenyl bisphenol diglycidyl ether in N,N-dimethylformamide and mix it with 71.4g of flame-retardant functionalized boron nitride nanosheet dispersion. Stir for 1h, sonicate for 1h, then distill under reduced pressure at 60℃ for at least 30 minutes to remove most of the solvent, and then place it in a vacuum oven at 60℃ overnight to obtain a mixture of flame-retardant functionalized boron nitride nanosheets and epoxy resin.

[0113] (5) Add 2.1g of curing agent 4,4-diaminodiphenylmethane to the mixture obtained in step (4), mix evenly and degas, then add the mixture to a stainless steel mold, and cure it by hot pressing for 2h at 100℃ and 2MPa pressure using a flat vulcanizing machine. Then place it in an oven and cure it at 160℃ for 4h to obtain a thermally conductive and flame-retardant liquid crystal epoxy resin boron nitride nanosheet composite material with a filler content of 10wt%.

[0114] Example 8

[0115] An epoxy resin boron nitride nanosheet composite material. This epoxy resin boron nitride nanosheet composite material includes an epoxy resin matrix and flame-retardant functionalized boron nitride nanosheets filled in the epoxy resin matrix. Hexagonal boron nitride is exfoliated into few-layer boron nitride nanosheets using a flame-retardant-assisted ball milling exfoliation method. Simultaneously, the flame retardant is adsorbed onto the surface of the boron nitride nanosheets through π-π interactions or electrostatic interactions. The resulting flame-retardant functionalized boron nitride nanosheets are then used as thermally conductive and flame-retardant fillers in the epoxy resin matrix. The flame retardant is diethyl phenylphosphonate; the epoxy resin is a bisphenol A type epoxy resin; and the flame-retardant-modified boron nitride nanosheets in the epoxy resin matrix account for 10% of the total mass of the composite material.

[0116] The preparation method of the epoxy resin boron nitride nanosheet composite material includes the following steps:

[0117] (1) Place 1g of hexagonal boron nitride with a horizontal dimension of about 1μm, 60g of diethyl phenylphosphonate, 50g of zirconium oxide grinding balls with a diameter of 10mm and 90g of zirconium oxide grinding balls with a diameter of 2-4mm in a polytetrafluoroethylene grinding jar, fix the grinding jar in a planetary ball mill, and grind at a speed of 300rpm for 20 hours.

[0118] (2) The ball milling product obtained in step (1) is dispersed in dichloromethane, sonicated for 0.5 h, stirred for 0.5 h, and washed and filtered with dichloromethane to remove free flame retardant, so as to obtain flame-retardant functionalized boron nitride nanosheets.

[0119] (3) Disperse the flame-retardant functionalized boron nitride nanosheets obtained in step (2) into ethyl acetate, sonicate for 1 h, stir for 1 h, and obtain a dispersion of flame-retardant functionalized boron nitride nanosheets with a concentration of 14 mg / g.

[0120] (4) Dissolve 4.9g of bisphenol A epoxy resin in ethyl acetate and mix it with 71.4g of flame-retardant functionalized boron nitride nanosheet dispersion. Stir for 1h, sonicate for 1h, then distill under reduced pressure at 60℃ for at least 30 minutes to remove most of the solvent, and then place it in a vacuum oven at 60℃ overnight to obtain a mixture of flame-retardant functionalized boron nitride nanosheets and epoxy resin.

[0121] (5) Add 4g of methylhexahydrophthalic anhydride and 0.1g of N-N'-dimethylbenzylamine to the above mixture and mix evenly. Then, cast the mixture into a polytetrafluoroethylene mold and place it in an oven. Treat it at 135°C for 1 hour and cure it at 145°C for 2 hours to obtain a thermally conductive and flame-retardant epoxy resin boron nitride nanosheet composite material with a filler content of 10wt%.

[0122] Comparative Example 1

[0123] A pure epoxy resin material was prepared. The epoxy resin was bisphenol F type epoxy resin. 1.2 g of 2-ethyl-4-methylimidazole and 20 g of bisphenol F type epoxy resin were mixed evenly and degassed, then cast into a polytetrafluoroethylene mold and placed in an oven for curing. The curing conditions were 60°C for 2 hours and then 150°C for 8 hours.

[0124] Comparative Example 2

[0125] An epoxy resin hexagonal boron nitride composite material was prepared. This epoxy resin hexagonal boron nitride composite material comprises an epoxy resin matrix and hexagonal boron nitride filled within the epoxy resin matrix. The epoxy resin is a bisphenol F type epoxy resin; the hexagonal boron nitride in the epoxy resin matrix accounts for 5% of the total mass of the composite material.

[0126] The preparation method of the epoxy resin hexagonal boron nitride composite material includes the following steps:

[0127] (1) 1.1 g of hexagonal boron nitride with a horizontal size of about 10 μm was dispersed in 100 mL of acetone, sonicated for 1 h, and stirred for 1 h to obtain a dispersion of hexagonal boron nitride.

[0128] (2) Add 20g of epoxy resin to the dispersion of hexagonal boron nitride obtained in step (1), stir for 1h, sonicate for 1h, then distill under reduced pressure at 60°C for at least 30 minutes to remove most of the solvent, and then place in a vacuum oven at 60°C overnight to obtain a mixture of hexagonal boron nitride and epoxy resin.

[0129] (3) Add 1.2g of curing agent 2-ethyl-4-methylimidazole to the mixture obtained in step (2), mix evenly and degas, then cast it into a polytetrafluoroethylene mold and place it in an oven for curing reaction. The curing reaction conditions are 60℃ for 2h and 150℃ for 8h.

[0130] Comparative Example 3

[0131] An epoxy resin hexagonal boron nitride composite material was prepared. This epoxy resin hexagonal boron nitride composite material comprises an epoxy resin matrix and hexagonal boron nitride filled within the epoxy resin matrix. The epoxy resin is a bisphenol F type epoxy resin; the hexagonal boron nitride in the epoxy resin matrix accounts for 10% of the total mass of the composite material.

[0132] The preparation method of the epoxy resin hexagonal boron nitride composite material includes the following steps:

[0133] (1) 2.4 g of hexagonal boron nitride with a horizontal size of about 10 μm was dispersed in 150 mL of acetone, sonicated for 1 h, and stirred for 1 h to obtain a dispersion of hexagonal boron nitride.

[0134] (2) Add 20g of epoxy resin to the dispersion of hexagonal boron nitride obtained in step (1), stir for 1h, sonicate for 1h, then distill under reduced pressure at 60°C for at least 30 minutes to remove most of the solvent, and then place in a vacuum oven at 60°C overnight to obtain a mixture of hexagonal boron nitride and epoxy resin.

[0135] (3) Add 1.2g of curing agent 2-ethyl-4-methylimidazole to the mixture obtained in step (2), mix evenly and degas, then cast it into a polytetrafluoroethylene mold and place it in an oven for curing reaction. The curing reaction conditions are 60℃ for 2h and 150℃ for 8h.

[0136] Comparative Example 4

[0137] An epoxy resin hexagonal boron nitride composite material was prepared. This epoxy resin hexagonal boron nitride composite material comprises an epoxy resin matrix and hexagonal boron nitride filled within the epoxy resin matrix. The epoxy resin is a bisphenol F type epoxy resin; the hexagonal boron nitride in the epoxy resin matrix accounts for 20% of the total mass of the composite material.

[0138] The preparation method of the epoxy resin hexagonal boron nitride composite material includes the following steps:

[0139] (1) 5.3g of hexagonal boron nitride with a horizontal size of about 10μm was dispersed in 400mL of acetone, sonicated for 1h, and stirred for 1h to obtain a dispersion of hexagonal boron nitride.

[0140] (2) Add 20g of epoxy resin to the hexagonal boron nitride dispersion obtained in step (1), stir for 1h, sonicate for 1h, then distill under reduced pressure at 60℃ for at least 30 minutes to remove most of the solvent, and then place in a vacuum oven at 60℃ overnight to obtain a mixture of hexagonal boron nitride epoxy resin.

[0141] (3) Add 1.2g of curing agent 2-ethyl-4-methylimidazole to the mixture obtained in step (2), mix evenly and degas, then cast it into a polytetrafluoroethylene mold and place it in an oven for curing reaction. The curing reaction conditions are 60℃ for 2h and 150℃ for 8h.

[0142] Comparative Example 5

[0143] An epoxy resin hexagonal boron nitride composite material was prepared. This epoxy resin hexagonal boron nitride composite material comprises an epoxy resin matrix and hexagonal boron nitride filled within the epoxy resin matrix. The epoxy resin is a bisphenol F type epoxy resin; the hexagonal boron nitride in the epoxy resin matrix accounts for 30% of the total mass of the composite material.

[0144] The preparation method of the epoxy resin hexagonal boron nitride composite material includes the following steps:

[0145] (1) 9.1g of hexagonal boron nitride with a horizontal size of about 10μm was dispersed in 650mL of acetone, sonicated for 1h, and stirred for 1h to obtain a dispersion of hexagonal boron nitride.

[0146] (2) Add 20g of epoxy resin to the dispersion of hexagonal boron nitride obtained in step (1), stir for 1h, sonicate for 1h, then distill under reduced pressure at 60°C for at least 30 minutes to remove most of the solvent, and then place in a vacuum oven at 60°C overnight to obtain a mixture of hexagonal boron nitride and epoxy resin.

[0147] (3) Add 1.2g of curing agent 2-ethyl-4-methylimidazole to the mixture obtained in step (2), mix evenly and degas, then cast it into a polytetrafluoroethylene mold and place it in an oven for curing reaction. The curing reaction conditions are 60℃ for 2h and 150℃ for 8h. Morphology and structural characterization of flame-retardant functionalized boron nitride nanosheets:

[0148] Figure 1 These are transmission electron microscopy (TEM) images of the phenylphosphonic acid-modified boron nitride nanosheets prepared in Examples 1-4. Due to the significant reduction in thickness, the phenylphosphonic acid-modified boron nitride nanosheets are transparent and exhibit bending and folding phenomena, with a relatively disordered structure and indistinct edges. This structure can be attributed to mechanochemical exfoliation-induced fracture and phenylphosphonic acid molecular functionalization. Figure 2These are the elemental energy distribution (EED) spectra of the phenylphosphonic acid-modified boron nitride nanosheets prepared in Examples 1-4. It can be seen that phosphorus (P) is uniformly distributed on the boron nitride nanosheets, indicating that phenylphosphonic acid was successfully modified onto the surface of the boron nitride nanosheets. Uniformity and thermal conductivity performance testing:

[0149] Comparison of the packing dispersion effects in Example 1 and Comparative Example 1 Figure 3 and Figure 4 As shown, where, Figure 3 The image shown is a scanning electron microscope image of the filler dispersion in Example 1. It can be seen that the flame retardant-modified boron nitride nanosheets are uniformly distributed in the epoxy resin matrix, which is beneficial for the construction of the thermally conductive network. Figure 4 The image shows a scanning electron microscope (SEM) image of the dispersion of unmodified hexagonal boron nitride in epoxy resin. It can be seen that hexagonal boron nitride exhibits obvious aggregation in epoxy resin. Figure 5 The image shown is a cross-sectional scanning electron microscope image of the epoxy resin flame-retardant functionalized boron nitride nanosheet composite material in Example 2. It can be seen that the boron nitride nanosheets form a network in the epoxy resin matrix, which is beneficial to improving the thermal conductivity of the composite material. Figure 6 The results show that the epoxy resin flame-retardant functionalized boron nitride nanosheet composite material has a higher thermal conductivity compared to the epoxy resin hexagonal boron nitride composite material. It is evident that surface modification of the boron nitride nanosheets with flame retardants improves the interfacial compatibility between the boron nitride nanosheets and the epoxy resin, thereby effectively improving the thermal conductivity. This improvement becomes increasingly pronounced with increasing filler content (e.g., ...). Figure 6 As shown, when the filler content is greater than 5 wt%, the difference in thermal conductivity between the epoxy resin hexagonal boron nitride composite material and the epoxy resin flame-retardant functionalized boron nitride nanosheet composite material increases with the increase of filler content.

[0150] Mechanical property testing:

[0151] Generally, in practical applications, thermal interface materials need to possess good mechanical properties. The bending properties of the prepared composite material were studied through bending tests, and the results are as follows: Figure 7As shown in the figure. Since the intrinsic modulus of boron nitride is higher than that of epoxy resin, the flexural modulus of the composite material increased from 5.6 GPa in epoxy resin to 8.0 GPa and 9.7 GPa, respectively, after adding hexagonal boron nitride or phenylphosphonic acid-modified boron nitride nanosheets to epoxy resin. Notably, the flexural strength and modulus of the epoxy resin flame-retardant functionalized boron nitride nanosheet composite material are superior to those of the epoxy resin hexagonal boron nitride composite material, mainly due to the stronger interaction between the epoxy resin matrix and the flame-retardant functionalized boron nitride nanosheets. Furthermore, the adhesive properties of thermal interface materials are crucial for reducing the interfacial thermal resistance between heat sinks and electronic devices. The adhesion ability of epoxy resin, epoxy resin hexagonal boron nitride composite material, and epoxy resin flame-retardant functionalized boron nitride nanosheet composite material to a stainless steel matrix was evaluated through lap shear tests. Figure 8 The average bond strength of the epoxy resin flame-retardant functionalized boron nitride nanosheet composite material is 37.1 MPa, which is higher than that of epoxy resin and epoxy resin hexagonal boron nitride composite material.

[0152] Flame retardant performance testing:

[0153] The maximum heat release rate, total heat release, maximum smoke release rate, and total smoke release of the composite materials provided in Example 1, Comparative Example 1, and Comparative Example 2 were measured using a cone calorimeter. The relevant results are shown in Table 1.

[0154] Table 1 Comparison of relevant performance indicators of the material of the present invention with those of the prior art.

[0155]

[0156] Note: Comparative Example 1 in the table is pure bisphenol F epoxy resin.

[0157] Comparative Example 2 is an epoxy resin hexagonal boron nitride composite material, with hexagonal boron nitride as the filler, and the addition amount is 5wt%.

[0158] Example 1 is an epoxy resin flame-retardant functionalized boron nitride nanosheet composite material, with phenylphosphonic acid modified boron nitride nanosheets added at a rate of 5 wt%.

[0159] Table 1 shows that, compared with pure epoxy resin and epoxy resin hexagonal boron nitride nanosheet composites, the epoxy resin flame-retardant functionalized boron nitride nanosheet composites exhibit significantly lower maximum heat release rate, total heat release, maximum smoke release rate, and total smoke release. The flame retardant modified on the surface of the boron nitride nanosheets not only improves the interfacial compatibility between the boron nitride nanosheets and epoxy resin but also endows the composite material of this invention with excellent flame-retardant properties.

[0160] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An epoxy resin / boron nitride nanosheet composite material, characterized in that, The invention comprises an epoxy resin matrix and boron nitride nanosheets modified with flame retardants dispersed in the epoxy resin matrix; wherein the mass ratio of the epoxy resin matrix to the boron nitride nanosheets modified with flame retardants is 60:40 to 95:5; the flame retardant on the surface of the boron nitride nanosheets modified with flame retardants is adsorbed on the surface of the boron nitride nanosheets through physical interactions such as π-π interactions or electrostatic interactions, and the flame retardant is a phosphorus-containing organic compound with a benzene ring; The epoxy resin / boron nitride nanosheet composite material, compared to the epoxy resin matrix itself, has not only better flame retardancy but also better thermal conductivity. The flame-retardant-modified boron nitride nanosheets are prepared by a method including the following steps: (1) placing hexagonal boron nitride, flame retardant and grinding balls in a ball mill jar and performing dry ball milling; (2) dispersing the ball milling product obtained in step (1) in a solvent and washing it with the solvent to remove the free flame retardant, thereby obtaining flame-retardant-modified boron nitride nanosheets.

2. The epoxy resin / boron nitride nanosheet composite material as described in claim 1, characterized in that, The flame retardant is one or more of phenylphosphonic acid, phenylphosphonous acid, diethyl phenylphosphonate, and diphenylphosphonic acid.

3. The epoxy resin / boron nitride nanosheet composite material as described in claim 1, characterized in that, The epoxy resin matrix is ​​bisphenol A type epoxy resin, bisphenol F type epoxy resin, or liquid crystal epoxy resin.

4. The method for preparing the epoxy resin / boron nitride nanosheet composite material according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Place hexagonal boron nitride, flame retardant and grinding balls in a ball mill jar and perform dry ball milling; (2) The ball milling product obtained in step (1) is dispersed in a solvent and washed with the solvent to remove the free flame retardant, thereby obtaining boron nitride nanosheets modified with flame retardant. (3) Disperse the flame-retardant-modified boron nitride nanosheets obtained in step (2) into a solvent to obtain a dispersion of flame-retardant-modified boron nitride nanosheets. (4) Dissolve the epoxy resin in a solvent, then mix it thoroughly with the dispersion of boron nitride nanosheets modified with flame retardant, and then remove the solvent to obtain a mixture of boron nitride nanosheets modified with flame retardant and epoxy resin. (5) Add the curing agent to the mixture obtained in step (4), mix evenly and degas, and after curing reaction, epoxy resin / boron nitride nanosheet composite material can be obtained.

5. The preparation method according to claim 4, characterized in that, In step (1), the particle size of the hexagonal boron nitride is 1 μm to 10 μm; the flame retardant is one or more of phenylphosphonic acid, phenylphosphonous acid, diethyl phenylphosphonate, and diphenylphosphonic acid; the mass ratio of the hexagonal boron nitride to the flame retardant is 1:1 to 1:60; and the grinding balls are selected from agate grinding balls or zirconium oxide grinding balls with a diameter of 2 to 10 mm.

6. The preparation method according to claim 4, characterized in that, In steps (2) and (3), the dispersion is specifically achieved by one or more of ultrasonic treatment, magnetic stirring, and mechanical stirring.

7. The preparation method according to claim 4, characterized in that, In step (2), the solvent is one or more of deionized water, ethanol, dichloromethane, and acetone; In steps (3) and (4), the solvent is a solvent capable of dissolving epoxy resin.

8. The preparation method according to claim 7, characterized in that, In steps (3) and (4), the solvent is one or more of dichloromethane, acetone, chloroform, N,N-dimethylformamide, and ethyl acetate.

9. The preparation method according to claim 4, characterized in that, In step (4), the solvent removal is specifically carried out by one or more of the following methods: vacuum distillation, vacuum drying, and heat drying.

10. The preparation method according to claim 4, characterized in that, The curing agent includes imidazole curing agents, amine curing agents, or acid anhydride curing agents.

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