Composite material with isolation structure as well as preparation method and application of composite material

Abstract

The invention belongs to the field of composite materials, and relates to a composite material with an isolation structure and a preparation method and application thereof. The composite material with the isolation structure comprises a thermoplastic polymer matrix and a heat-conducting filler filled in the thermoplastic polymer matrix, the heat-conducting filler comprises thermoplastic polymer microspheres and a heat-conducting material coating layer formed on the surfaces of the thermoplastic polymer microspheres through electrostatic interaction. The composition of the thermoplastic polymer microspheres in the selected thermoplastic polymer matrix and the heat-conducting filler is the same or similar, and the batch performance stability can be improved while it is guaranteed that the composite material forms an isolation structure.

Description

Technical Field

[0001] The invention belongs to the field of composite materials, and relates to a composite material with an isolation structure, a preparation method and an application thereof. Background Art

[0002] 5G communications equipment and electronic devices are moving towards miniaturization, high integration, and lightweighting, leading to increasingly serious heat buildup. Polymers, due to their diverse functionality, lightweight, low cost, excellent chemical stability, ease of processing, and corrosion resistance, have become a promising candidate for high-performance heat dissipation materials. Low intrinsic thermal conductivity is a key limitation to the development of polymers. Creating thermally conductive polymer-based composites by constructing a filler network within polymers is an effective strategy for improving their thermal conductivity.

[0003] Compared to one-dimensional and three-dimensional fillers, sheet-like two-dimensional fillers are easier to overlap with each other, and at a lower filling amount, a complete and continuous thermal conductive network can be constructed within the polymer matrix, thereby effectively improving the thermal conductivity of the polymer. Commonly used two-dimensional fillers for thermal conductive fillers include graphene (GR), boron nitride (BNNS), etc. However, the two-dimensional planar structure with a high aspect ratio is very easy to orient along the planar direction in the polymer matrix. The ultra-high thermal conductivity value is limited to the in-plane direction, and the improvement in inter-plane thermal conductivity, which is more important for effective heat dissipation, is very small or even negligible. In the application process, good results have not been achieved, and research progress is limited. The effect is even worse when the filler agglomerates.

[0004] Currently, constructing a three-dimensional thermally conductive filler network through the design and optimization of an isolation structure has become a highly effective method for improving thermal conductivity. This structure typically utilizes highly conductive materials (such as carbon nanofibers and metal fillers) selectively distributed within a polymer matrix to form a continuous thermal pathway, enabling efficient heat transfer with low thermal resistance. For two-dimensional fillers, the isolation structure effectively eliminates agglomeration, significantly improving the material's overall thermal conductivity.

[0005] Traditional preparation methods such as solution method, emulsion method, in-situ polymerization method, binder mixing method, laser selective sintering method, etc., for preparing thermal conductive composite materials with isolation structure require strict control of processing conditions to prevent filler migration, which increases the complexity and cost of the process. For example, Patent Document 1 (CN 117924795 A) discloses a preparation method for a high thermal conductive composite material with isolation structure, which mainly utilizes the self-expansion of expansion agent microspheres containing alkane gas inside to successfully form an isolation structure, but there are the following problems: (1) The selected matrix is ​​epoxy resin, which requires not only the addition of a curing agent to achieve the curing of the epoxy resin, but also a vacuum degassing process, making the preparation method more complicated; (2) The surface structure of the used expansion microspheres will lead to poor dispersion of the two-dimensional material on the surface of the microspheres, making it difficult to distribute evenly, and the large volume of the expansion microspheres will increase the gaps between the fillers, thereby affecting the overall performance of the composite material (such as thermal conductivity, electrical conductivity, etc.); (3) The surface hydrophilicity of the expansion microspheres is poor, which may limit their application in certain water-based systems; (4) The expansion agent microspheres contain alkane gas, which has the risk of leakage. Therefore, it is urgent to explore more convenient, economical and safe methods to construct isolation structures to further improve the thermal conductivity of composite materials and the performance stability of batch composite materials. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a composite material with an isolation structure, a preparation method thereof, and an application thereof.

[0007] One aspect of the present invention provides a composite material having an isolation structure, comprising: A thermoplastic polymer matrix and a heat-conducting filler filled in the thermoplastic polymer matrix; the heat-conducting filler comprises thermoplastic polymer microspheres and a heat-conducting material coating layer formed on the surface of the thermoplastic polymer microspheres through electrostatic action.

[0008] In the present invention, a thermally conductive filler is used to form a thermally conductive material coating layer on the surface of thermoplastic polymer microspheres through electrostatic action to improve the thermal conductivity of the composite material, while controlling the composition of the thermoplastic polymer matrix and the thermoplastic polymer microspheres in the thermally conductive filler to be the same or similar, thereby improving the performance stability of the resulting batch composite material while ensuring the formation of an isolation structure. Wherein, the meaning of the isolation structure in this application is the thermally conductive material coating layer of graphene-coated polystyrene microspheres formed by hot pressing. Specifically, graphene is uniformly coated on the surface of the polystyrene microspheres through electrostatic action, and these microspheres are tightly combined with the thermally conductive filler through a hot pressing process to form an effective isolation layer, which changes the graphene orientation to form a three-dimensional heat-conducting channel. The focus of the present invention is to ensure the uniform distribution of the filler and the good combination of the thermoplastic matrix through the uniform coating layer formed after hot pressing.

[0009] Preferably, the thermoplastic polymer matrix comprises at least one of polystyrene PS, polymethyl methacrylate PMMA, polypropylene PP, polyethylene PE, and polyethylene terephthalate PET.

[0010] Preferably, the thermoplastic polymer microspheres include at least one of polystyrene microspheres, polymethyl methacrylate microspheres, polypropylene microspheres, polyethylene microspheres, and polyethylene terephthalate microspheres.

[0011] Preferably, the surfaces of the thermoplastic polymer microspheres and the thermal conductive material in the thermal conductive material coating layer are respectively loaded with oppositely charged groups; preferably, the surfaces of the thermoplastic polymer microspheres are loaded with positively charged groups, and the surface of the thermal conductive material in the thermal conductive material coating layer is loaded with negatively charged groups.

[0012] More preferably, the negatively charged groups include carboxyl (-COO-), sulfonic acid (-SO3 - ), hydroxyl group (-O - ) at least one of the following.

[0013] More preferably, the positively charged group comprises a proton (H + ), dialkylamino (-NR2), alkylamino (-NHR), amino (-NH2), and at least one of an organic phosphorus group.

[0014] Preferably, the mass ratio of the thermal conductive material coating layer to the thermoplastic polymer microspheres is 1:(5-100). Within this mass ratio range, the thermal conductivity of the resulting composite material is significantly improved.

[0015] Preferably, the mass ratio of the thermoplastic polymer matrix to the thermally conductive filler is (1-20):1, more preferably (1-3):1. Within this mass ratio range of the thermoplastic polymer matrix to the thermally conductive filler, the resulting composite material exhibits significantly improved thermal conductivity, mechanical properties, and uniformity.

[0016] Preferably, the particle size of the thermoplastic polymer microspheres is 1 μm to 100 μm; preferably, the thermoplastic polymer microspheres have a hollow structure, and the wall thickness of the thermoplastic polymer microspheres is at least 5%, preferably 10% to 50%, of the particle size of the thermoplastic polymer microspheres.

[0017] Preferably, the thermally conductive material in the thermally conductive material coating layer is a two-dimensional thermally conductive material, preferably selected from at least one of graphene, graphite nanosheets, hexagonal boron nitride nanosheets, boron nitride nanotubes, two-dimensional transition metal carbides, two-dimensional transition metal nitrides, two-dimensional transition metal carbonitrides (MXene), single-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0018] Preferably, the composite material with an isolation structure has one or more of the following characteristics: The inter-plane thermal conductivity of the composite material with the isolation structure measured by laser flash method is ≥3.0 W / (m·K), preferably 3.0~5.0 W / (m·K); The tensile strength of the composite material with the isolation structure measured by a universal testing machine is 30-40 MPa; The decomposition temperature of the composite material with the isolation structure measured by a synchronous thermal analyzer is 400°C to 450°C. A second aspect of the present invention provides a method for preparing a composite material having an isolation structure, the method comprising the following steps: (1) Dispersing thermoplastic polymer microspheres and thermal conductive materials respectively loaded with oppositely charged groups on their surfaces in an organic solvent free of charge aggregation and drying them to obtain a thermal conductive filler; preferably, the surfaces of the thermoplastic polymer microspheres are loaded with positively charged groups, and the surface of the thermal conductive material is loaded with negatively charged groups; (2) The thermal conductive filler is subjected to hot pressing to obtain a composite material with an isolation structure.

[0019] In the present invention, it is preferred to mix thermoplastic polymer microspheres with positively charged groups on the surface and thermally conductive materials with negatively charged groups on the surface to prepare thermally conductive fillers, which are then subjected to hot pressing. The resulting composite material has an isolation structure and excellent thermal conductivity.

[0020] Preferably, the positively charged group comprises a proton (H + ), dialkylamino (-NR2), alkylamino (-NHR), amino (-NH2), at least one of an organophosphorus group; And / or, the negatively charged groups include carboxyl (-COO-), sulfonic acid (-SO3 - ), hydroxyl group (-O - ) at least one of the following.

[0021] Preferably, the thermoplastic polymer microspheres meet one or more of the following characteristics: The thermoplastic polymer microspheres include at least one of polystyrene microspheres, polymethyl methacrylate microspheres, polypropylene microspheres, polyethylene microspheres, and polyethylene terephthalate microspheres; The particle size of the thermoplastic polymer microspheres is 1 μm to 100 μm; The thermoplastic polymer microspheres have a hollow structure, and the wall thickness of the thermoplastic polymer microspheres is at least 5%, preferably 10% to 50%, of the particle size of the thermoplastic polymer microspheres.

[0022] Preferably, the thermally conductive material is a two-dimensional thermally conductive material, preferably at least one selected from graphene, graphite nanosheets, hexagonal boron nitride nanosheets, boron nitride nanotubes, two-dimensional transition metal carbides, two-dimensional transition metal nitrides, two-dimensional transition metal carbonitrides, single-walled carbon nanotubes, and multi-walled carbon nanotubes; And / or, the mass ratio of the thermal conductive material to the thermoplastic polymer microspheres is 1:(5-100).

[0023] Preferably, in step (2), the parameters of the hot pressing treatment include: pressure of 2.08 MPa to 10.4 MPa, temperature of 100 to 150°C, and time of 30 to 90 min.

[0024] A third aspect of the present invention provides a method for preparing a composite material having an isolation structure, the method comprising the following steps: (1) Dispersing thermoplastic polymer microspheres and thermal conductive materials respectively loaded with oppositely charged groups on their surfaces in an organic solvent free of charge aggregation and drying them to obtain a thermal conductive filler; preferably, the surfaces of the thermoplastic polymer microspheres are loaded with positively charged groups, and the surface of the thermal conductive material is loaded with negatively charged groups; (2) The thermal conductive filler and the thermoplastic polymer matrix are mixed and then subjected to hot pressing to obtain a composite material with an isolation structure.

[0025] In this invention, electrostatic action is first used to uniformly and tightly coat the surface of thermoplastic polymer microspheres with a thermally conductive material (preferably a two-dimensional thermally conductive material, i.e., the two-dimensional thermally conductive material is tightly coated on the surface of the thermoplastic polymer microspheres). This inhibits the aggregation and orientation of the two-dimensional thermally conductive material, reduces interfacial thermal resistance, and significantly improves thermal conductivity. Then, through hot pressing, an isolation structure network is constructed, allowing the two-dimensional thermally conductive material coated on the surface of the thermoplastic polymer microspheres to serve as a thermal channel, providing high thermal conductivity. Ultimately, the thermal conductivity of the filler can be significantly improved while adding a relatively low amount of the two-dimensional thermally conductive material.

[0026] Preferably, in step (1): the surface of the thermoplastic polymer microspheres is loaded with positively charged groups, and the surface of the thermal conductive material is loaded with negatively charged groups.

[0027] More preferably, the positively charged group comprises a proton (H + ), dialkylamino (-NR2), alkylamino (-NHR), amino (-NH2), at least one of an organophosphorus group; And / or, the negatively charged groups include carboxyl (-COO-), sulfonic acid (-SO3 - ), hydroxyl group (-O - ) at least one of the following.

[0028] Preferably, the thermoplastic polymer microspheres meet one or more of the following characteristics: The thermoplastic polymer microspheres include at least one of polystyrene microspheres, polymethyl methacrylate microspheres, polypropylene microspheres, polyethylene microspheres, and polyethylene terephthalate microspheres; The particle size of the thermoplastic polymer microspheres is 1 μm to 100 μm; The thermoplastic polymer microspheres have a hollow structure, and the wall thickness of the thermoplastic polymer microspheres is at least 5%, preferably 10% to 50%, of the particle size of the thermoplastic polymer microspheres.

[0029] Preferably, the thermally conductive material is a two-dimensional thermally conductive material, preferably at least one selected from graphene, graphite nanosheets, hexagonal boron nitride nanosheets, boron nitride nanotubes, two-dimensional transition metal carbides, two-dimensional transition metal nitrides, two-dimensional transition metal carbonitrides, single-walled carbon nanotubes, and multi-walled carbon nanotubes; And / or, the mass ratio of the thermal conductive material to the thermoplastic polymer microspheres is 1:(5-100).

[0030] Preferably, in step (2): the thermoplastic polymer matrix comprises at least one of polystyrene PS, polymethyl methacrylate PMMA, polypropylene PP, polyethylene PE, and polyethylene terephthalate PET; And / or, the mass ratio of the thermoplastic polymer matrix to the thermal conductive filler is (1-20):1, preferably (1-3):1.

[0031] Preferably, in step (2), the parameters of the hot pressing treatment include: pressure of 2.08 MPa to 10.4 MPa, temperature of 100 to 150°C, and time of 30 to 90 min.

[0032] A fourth aspect of the present invention provides a composite material having an isolation structure prepared according to the above preparation method.

[0033] A fifth aspect of the present invention provides an application of the composite material with the isolation structure in the field of heat conduction.

[0034] Beneficial effects of the present invention: 1. This invention achieves tight encapsulation of thermoplastic spherical particles with a two-dimensional thermally conductive material through strong electrostatic interactions. The resulting composite high-thermal conductivity filler overcomes the drawbacks of using two-dimensional thermally conductive materials or polymer spherical particles alone. Furthermore, through the design of an isolated structure, clear thermal conduction paths can be formed within the composite material, allowing heat to be efficiently transferred along these paths, thereby improving the overall thermal conductivity of the material.

[0035] 2. The present invention has good universal applicability. Raw materials are widely available, and there are a rich variety of low-dimensional fillers and thermoplastic microspheres to choose from. The preparation conditions are mild, the production efficiency is high, and it is easy to produce on a large scale. The prepared composite thermal conductive filler has a wide range of applications and can be used with polymer materials of various forms and compositions, and is suitable for common molding and processing equipment and processes.

[0036] 3. The present invention has good processing characteristics. During the hot pressing process, the low glass transition temperature of the thermoplastic material gives it good fluidity and processing characteristics. Through appropriate processing temperature and control conditions, dense bonding of the composite material can be achieved;

[0037] 4. The composite thermally conductive filler prepared by the present invention exhibits excellent overall performance. In addition to significantly improving the thermal conductivity of polymer materials, the introduction of composite thermally conductive fillers is expected to enhance their thermal stability and electrical insulation properties. This has broad application prospects in fields requiring high overall material performance, such as aviation, aerospace, and high-tech electronics and electrical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Flowchart of a method for preparing a composite material with an isolation structure according to the present invention; Figure 2 This is the SEM image of the uncoated polystyrene microspheres in Example 1; Figure 3 This is an SEM image of the polystyrene microspheres coated with the two-dimensional thermal conductive material in Example 1; Figure 4 This is an SEM image of the cross section of the composite material with an isolation structure prepared in Example 1. DETAILED DESCRIPTION

[0039] The present invention is further described below through the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, rather than to limit the present invention.

[0040] The composite material with an isolation structure disclosed in the present invention comprises: a thermoplastic polymer matrix, and a thermally conductive filler filled in the thermoplastic polymer matrix; the thermally conductive filler comprises thermoplastic polymer microspheres and a thermally conductive material coating layer formed on the surface of the thermoplastic polymer microspheres by electrostatic action.

[0041] In this invention, by adding a thermally conductive filler of the same or similar composition to the thermoplastic polymer matrix, the entire preparation process is not only easier to control, but also helps maintain material uniformity, reducing performance fluctuations caused by material inhomogeneity. More importantly, using the same material for the thermally conductive filler and the thermoplastic polymer matrix forms an effective thermal conductivity network, significantly reducing phonon scattering at the interface between the matrix and filler, and significantly improving the overall thermal conductivity of the material.

[0042] In one embodiment of the present invention, the thermoplastic polymer microspheres (or thermoplastic micron-shaped spherical particles, etc.) include at least one of PS microspheres, PMMA microspheres, PP microspheres, PE microspheres, and PET microspheres. The particle size of the thermoplastic polymer microspheres is 1 to 100 μm (e.g., 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc.). When the thermoplastic polymer microspheres have a hollow structure, the wall thickness of the thermoplastic polymer microspheres is 5% to 100% (excluding 100%) of the particle diameter, preferably 10% to 50% (e.g., 10, 20, 30, 40, 50), etc.

[0043] In one embodiment of the present invention, the thermally conductive material is a two-dimensional thermally conductive material, preferably including but not limited to: at least one of graphene, graphite nanosheets, hexagonal boron nitride nanosheets, boron nitride nanotubes, two-dimensional transition metal carbides, two-dimensional transition metal nitrides, two-dimensional transition metal carbonitrides (MXene), single-walled carbon nanotubes and multi-walled carbon nanotubes, or a combination thereof.

[0044] In a preferred embodiment of the present invention, the graphene has a diameter of 50 nm to 100 μm and a thickness of 1 to 100 nm. The graphite nanosheet has a diameter of 50 nm to 500 nm and a thickness of 1 to 100 nm. The hexagonal boron nitride nanosheet has a diameter of 50 nm to 10 μm and a thickness of 1 to 100 nm. The two-dimensional transition metal carbide has a diameter of 50 nm to 10 μm and a thickness of 5 to 50 nm. The two-dimensional transition metal nitride has a diameter of 50 nm to 10 μm and a thickness of 5 to 50 nm. The two-dimensional transition metal carbonitride (MXene) has a diameter of 50 nm to 10 μm and a thickness of 5 to 50 nm. The boron nitride nanotube has an inner diameter of 1 to 10 nm, an outer diameter of 5 to 50 nm, and a length of 100 to 10 nm. The single-walled carbon nanotube has an inner diameter of 0.5 to 2 nm, an outer diameter of 1 to 3 nm, and a length of 1 to 10 nm. The inner diameter of multi-walled carbon nanotubes is 2~10nm, the outer diameter is 5~50nm, and the length is 1~10nm.

[0045] In one embodiment of the present invention, the mass ratio of the thermal conductive material to the thermoplastic polymer microspheres is 1:5 to 1:100 (e.g., 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, 4:100, 4.5:100, 5:100).

[0046] In one embodiment of the present invention, the surfaces of the thermoplastic polymer microspheres and the thermal conductive material in the thermal conductive material coating layer are respectively loaded with oppositely charged groups. Preferably, the surfaces of the thermoplastic polymer microspheres are loaded with positively charged groups, and the surfaces of the thermal conductive material in the thermal conductive material coating layer are loaded with negatively charged groups. The negatively charged groups include carboxyl (-COO-), sulfonic acid (-SO3 - ), hydroxyl group (-O - ). The positively charged group comprises a proton (H + ), dialkylamino (-NR2), alkylamino (-NHR), amino (-NH2), and at least one of an organic phosphorus group.

[0047] In one embodiment of the present invention, the mass ratio of the thermoplastic polymer matrix to the thermally conductive filler is (1-20):1 (e.g., 0.5:1, 1:1, 2:1, 3:1, 4:1), preferably (1-3):1.

[0048] In the present invention, the electrostatic interaction between the two-dimensional thermally conductive material and the thermoplastic polymer microspheres is first used to achieve a tight encapsulation of the two, while simultaneously suppressing the aggregation and orientation of the two-dimensional thermally conductive material. Subsequently, the present invention forms a three-dimensional thermally conductive network through a simple molding process, namely hot pressing. This allows the thermally conductive material in the thermally conductive filler to more easily form continuous thermal conductive channels within the matrix, while simultaneously improving the thermal conductivity of the composite material both inter- and intra-plane, thereby reducing production costs. The following exemplifies the method for preparing a composite material with an isolation structure.

[0049] Preparation of thermally conductive fillers. First, oppositely charged groups are loaded onto the surfaces of a two-dimensional thermally conductive material and thermoplastic polymer microspheres. The two-dimensional thermally conductive material and thermoplastic polymer microspheres with oppositely charged groups are then dispersed and dried in an organic solvent free of charge aggregation to obtain a composite thermally conductive filler consisting of thermoplastic polymer microspheres coated with the two-dimensional thermally conductive material.

[0050] Graphene-coated polystyrene microspheres are used as an example.

[0051] Rich oppositely charged groups are loaded on the surface of graphene and polystyrene microspheres through the action of solvent.

[0052] In one embodiment of the present invention, negatively charged groups are loaded on the graphene surface. Negatively charged groups include but are not limited to: carboxyl (-COO - ), sulfonic acid group (-SO3 - ), hydroxyl (-O-), etc. For example, carboxyl (-COO - ) can be loaded by adding at least one of an oxidant (such as HNO3, H2O2) or an acidic solvent (such as sulfuric acid, phosphoric acid) or a combination thereof, or by specific methods such as oxidation and chemical vapor deposition. -) can be loaded by adding at least one of concentrated sulfuric acid (H2SO4), benzenesulfonic acid, alkylsulfonic acid, SO2, sulfonation reagent and H2O2 or a combination thereof or by sulfonation. - ) The loading can be achieved by adding at least one of NaOH, KOH, Ca(OH)2 and H2O2 or a combination thereof, or by hydration, hydrogenation treatment and other methods.

[0053] In one embodiment of the present invention, positively charged groups are loaded on the surface of polystyrene microspheres. Positively charged groups include but are not limited to: protons (H + ), dialkylamino (-NR2), alkylamino (-NHR), amino (-NH2), organic phosphorus group, etc. Proton (H + ) can be loaded by adding at least one of a strong acid (e.g., hydrochloric acid (HCl), sulfuric acid (H2SO4), hydrogen chloride gas (HCl), sodium bisulfate (NaHSO4), ammonium chloride (NH4Cl), and HF, or a combination thereof, or by acidic environment treatment. Dialkylamino groups (-NR2) can be loaded by adding at least one of a dialkylamine (e.g., dimethylamine, diethylamine), alkyl chlorides (e.g., methyl chloride, ethyl chloride), dialkylphosphites (e.g., dimethylphosphite), ammonia gas (NH3), and aminoalkylating agents (e.g., bromomethyl, bromoethyl, etc.), or a combination thereof, or by solvothermal methods. Alkylamino groups (-NHR) can be loaded by adding at least one of a alkylamine (e.g., methylamine, ethylamine), alkyl chlorides (e.g., methyl chloride, ethyl chloride), alkylamination agents (e.g., methyl chloride, ethyl chloride), amines (e.g., aminoethanol), or a combination thereof, or by chemical reaction methods. Amino groups (-NH2) can be loaded by adding at least one of ammonia (NH3), amines (such as aminoacetic acid, aminoethanol, etc.), aminoalkylating agents (such as chloroethylamine) and aminating agents (such as isocyanate) or a combination thereof, or by ammonia reaction method. As an example, the graphene surface is loaded with abundant hydroxyl groups (-OH - ) and loading abundant amino groups (-NH2) on the surface of polystyrene microspheres.

[0054] Negatively charged graphene and positively charged polystyrene microspheres are dispersed and dried in an organic solvent free of charge aggregation, achieving sufficient filler mixing and avoiding interference from the solvent charge, resulting in a thermally conductive filler. The mass ratio of graphene to polystyrene microspheres is 1:5 to 1:100.

[0055] It should be noted that the graphene mentioned above may also be replaced by hexagonal boron nitride (h-BN), graphite nanosheets, hexagonal boron nitride nanosheets (h-BNNS), boron nitride nanotubes, MXene, single-walled carbon nanotubes, multi-walled carbon nanotubes, etc. The thermoplastic polymer microspheres may be PE, PP, etc.

[0056] In one embodiment of the present invention, a thermoplastic polymer matrix and a thermally conductive filler are mixed and then hot-pressed to obtain a composite material with an insulating structure. The proportion of the thermally conductive filler in the composite material is controlled to be between 0% and 100%. The mass ratio of the thermoplastic polymer matrix to the thermally conductive filler is (1-20):1, preferably (1-3):1. Specifically, the hot press temperature is set to the glass transition temperature of the thermoplastic material, preheated, and after the temperature rises, graphene-coated polystyrene microspheres are placed in the hot press cavity. A pressing mold is placed above the filler. The pressure is set to 2kN to 10kN, the duration is set to 30 to 90 minutes, and the temperature is set to 100 to 150°C. The filler ratio is varied, and the filler and matrix are pre-dispersed and thoroughly mixed. For example, 10% graphene-coated polystyrene microspheres and 90% polystyrene are prepared using ultrasonic dispersion. The frequency of the ultrasonic dispersion is set to 30kHz. Mixing can be performed by rotary evaporation. The temperature of the rotary evaporator was set to 80°C and the vacuum was controlled at -0.1 to -0.4 bar. After mixing, the hot pressing process was repeated.

[0057] In a preferred embodiment of the present invention, when a thermally conductive filler is prepared using thermoplastic polymer microspheres with positively charged groups on their surfaces and a thermally conductive material with negatively charged groups on its surface, a composite material with an insulating structure and excellent thermal conductivity can be prepared without adding a thermoplastic polymer matrix. During this process, the thermoplastic polymer in the thermally conductive filler seeps through the conductive material coating, forming a bond, but the resulting mechanical properties are poor.

[0058] Performance testing method: The inter-plane thermal conductivity of the composite material with the isolation structure measured by laser flash method; The tensile strength of the composite material with an isolation structure measured using a universal testing machine method; Thermal stability of the composite material with an isolation structure measured by a simultaneous thermal analysis method; Performance uniformity: Take 30 samples from the same batch, test the thermal conductivity and take the average value. The performance fluctuation range is: ((minimum value - average value) / average value * 100% - 100%) to ((maximum value - average value) / average value * 100% - 100%).

[0059] The following examples are further given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description herein, and are not limited to the specific numerical values ​​exemplified below.

[0060] Example 1 1) Take 0.01g of graphene (25μm diameter × 6-8nm thickness) and add it to a ball mill, with the volume of graphene accounting for 1 / 3 of the volume of the ball mill and the volume of the grinding balls accounting for 1 / 3 of the volume of the ball mill. Set the speed of the planetary ball mill to 800rpm and ball mill for 12 hours. After the ball milling is completed, add the graphene to a mixed solution of 1mol / L NaOH solution and 30% H2O2 solution in a volume ratio of 1:1 (50mL in total) and heat under reflux at 100℃ for 6 hours. Then filter and collect the solid, adjust the vacuum degree of the vacuum oven to -0.6bar, and dry at 80℃ for 24 hours to obtain graphene loaded with negatively charged hydroxyl groups;

[0061] 2) 1 g of polystyrene microspheres (9-25 μm in size, with a wall thickness 10-30% of the thermoplastic polymer microsphere diameter) was added to a 0.01 mol / L KH-550 solution (γ-aminopropyltriethoxysilane solution) using a syringe pump at 0.03 mL / min. The mixture was heated under reflux at 70°C for 16 h. The solids were then collected by centrifugation and dried in a vacuum oven at -0.6 bar at 60°C for 24 h to obtain polystyrene microspheres loaded with positively charged amino groups.

[0062] 3) Add the negatively charged hydroxyl-loaded graphene obtained in 1) and the positively charged amino-loaded polystyrene microspheres obtained in 2) to 50 mL of acetone solvent and ultrasonicate at 30 kHz for 8 hours. Then, filter and collect the solids, rinsing with deionized water until the washings are neutral. Set the rotary evaporator temperature to 80°C and the vacuum level to -0.1 to -0.4 bar, and dry to obtain a thermally conductive filler comprising graphene-coated polystyrene microspheres.

[0063] 4) Take 1 g of thermal conductive filler and 0.5 g of polystyrene matrix and mix them evenly in a ratio of 2:1. Place them in a hot press, set the temperature to 120°C, adjust the pressure to 2 kN, and the pressure to 2.08 MPa. Maintain the pressure and heat for 60 minutes to obtain a PS / GR-PS composite material.

[0064] Example 2 The preparation process of this Example 2 refers to that of Example 1, with the main difference being that in step (4), the ratio of the thermal conductive filler of the graphene / polystyrene microsphere composite to the thermoplastic polymer matrix is ​​1:1, and 1 g of the thermal conductive filler is weighed and evenly mixed with 1 g of the polystyrene matrix.

[0065] Example 3 The preparation process of this Example 3 refers to that of Example 1, with the main difference being that in step (4), the ratio of the thermally conductive filler of the graphene / polystyrene microsphere composite to the thermoplastic polymer matrix is ​​3:1, and 3 g of the thermally conductive filler is weighed and evenly mixed with 1 g of the polystyrene matrix.

[0066] Example 4 The preparation process of this Example 4 refers to that of Example 1, with the main differences being that in step (1), the thermoplastic polymer microspheres are PMMA, and in step (4), the thermoplastic polymer matrix is ​​simultaneously changed to PMMA.

[0067] Example 5 The preparation process of this Example 5 refers to that of Example 1, with the main differences being that in step (1), the thermoplastic polymer microspheres are PP, and in step (4), the thermoplastic polymer matrix is ​​simultaneously changed to PP.

[0068] Example 6 The preparation process of Example 6 refers to that of Example 1, with the main differences being that in step (1), the thermoplastic polymer microspheres are PET, and in step (4), the matrix is ​​simultaneously changed to PET.

[0069] Example 7 The preparation process of this Example 7 refers to that of Example 1, with the main differences being that: in step (1), the two-dimensional sheet material is h-BN (diameter 100 nm~10 μm, thickness 1~10 nm); h-BN is added to a ball mill, the volume of h-BN is controlled to account for 1 / 3 of the volume of the ball mill, the volume of the grinding balls accounts for 1 / 3 of the volume of the ball mill, the speed of the planetary ball mill is set to 800 rpm, and the ball milling treatment is carried out for 12 h; the ball-milled h-BN is added to a mixture of 30% hydrogen peroxide solution and 1 mol / L sodium hydroxide solution (volume ratio of 1:1), and heated to reflux at 100°C for 6 h; then, the solid is filtered and collected, the vacuum degree of the vacuum oven is adjusted to -0.6 bar, and the temperature is 80°C for drying for 24 h to obtain h-BN loaded with negatively charged hydroxyl groups.

[0070] Example 8 The preparation process of this Example 8 refers to that of Example 1, with the main difference being that: in step (1), the two-dimensional sheet material is Ti3C2 (diameter 100 nm~10 μm, thickness 1~5 nm); Ti3C2 is added to a ball mill, the volume of Ti3C2 accounts for 1 / 3 of the volume of the ball mill, the volume of the grinding balls accounts for 1 / 3 of the volume of the ball mill, the speed of the planetary ball mill is set to 800 rpm, and the ball milling treatment is carried out for 12 h; the ball-milled Ti3C2 is added to a mixture of 30% hydrogen peroxide solution and 1 mol / L sodium hydroxide solution (volume ratio of 1:1), and heated under reflux at 100°C for 6 h; then, the solid is filtered and collected, and the vacuum degree of the vacuum oven is adjusted to -0.6 bar and the temperature is 80°C for drying for 24 h to obtain Ti3C2 loaded with negatively charged hydroxyl groups.

[0071] Example 9 The preparation process of this Example 9 refers to that of Example 1, with the main difference being that in step (4), the ratio of the thermally conductive filler of the graphene / polystyrene microsphere composite to the thermoplastic polymer matrix is ​​0.5:1, and 0.5 g of the thermally conductive filler is weighed and uniformly mixed with 1 g of the polystyrene matrix.

[0072] Example 10 The preparation process of this Example 10 refers to that of Example 1, with the main difference being that in step (4), the ratio of the thermal conductive filler of the graphene / polystyrene microsphere composite to the thermoplastic polymer matrix is ​​4:1, and 1 g of the thermal conductive filler is weighed and uniformly mixed with 1 g of the polystyrene matrix.

[0073] Example 11 The preparation process of this Example 11 refers to that of Example 1, with the main difference being that in step (4), the ratio of the thermally conductive filler of the graphene / polystyrene microsphere composite to the thermoplastic polymer matrix is ​​5:1, and 1 g of the thermally conductive filler is weighed and directly hot-pressed.

[0074] Example 12 The preparation process of this Example 12 refers to that of Example 1, with the main difference being that in step (1), 0.03 g of graphene (diameter 25 μm × thickness 6-8 nm) was taken.

[0075] Example 13 The preparation process of this Example 13 refers to that of Example 1, with the main difference being that in step (1), 0.05 g of graphene (diameter 25 μm × thickness 6-8 nm) was taken.

[0076] Example 14 The preparation process of this Example 14 refers to that of Example 1, with the main difference being that in step (4), the thermoplastic polymer matrix is ​​directly changed to PMMA, while the other steps remain unchanged.

[0077] Example 15 The preparation process of this Example 15 refers to that of Example 1, with the main difference being that in step (4), the thermoplastic polymer matrix is ​​directly changed to PP, and the other steps remain unchanged.

[0078] Example 16 The preparation process of this Example 16 refers to that of Example 1, with the main difference being that in step (4), the thermoplastic polymer matrix is ​​directly changed to PET, and the other steps remain unchanged.

[0079] Figure 2 This is an SEM image of the uncoated polystyrene microspheres in Example 1. It can be seen from the image that the uncoated polystyrene microspheres have a smooth surface without obvious particles or cracks on the surface.

[0080] Figure 3 This is an SEM image of the polystyrene microspheres coated with the two-dimensional thermal conductive material in Example 1. It can be seen from the image that there is a thin layer of flakes on the surface of the polystyrene microspheres, and the two-dimensional thermal conductive material is successfully coated or attached to the surface of the polystyrene microspheres.

[0081] Figure 4 This is an SEM image of the cross section of the composite material with an isolation structure prepared in Example 1. It can be seen from the image that the graphene is no longer aggregated and oriented, and the three-dimensional heat conduction path is more clear.

[0082] The performance parameters of Examples 1-14 of the present invention are shown in Table 1.

[0083] Table 1 Example Thermally conductive fillers Thermoplastic polymer matrix Thermally conductive fillers: thermoplastic polymer matrix Inter-surface thermal conductivity (W / (fm·K)) Tensile strength / MPa Volatility / % Example 9 GR@PS (1:100) PS 0.5：1 2.88 40 -5%~8% Example 2 GR@PS (1:100) PS 1：1 3.15 38 -3%~7% Example 1 GR@PS (1:100) PS 2：1 4.56 35 -5%~5% Example 3 GR@PS (1:100) PS 3：1 4.21 33 -5%~6% Example 10 GR@PS (1:100) PS 4：1 4.05 30 -5%~8% Example 11 GR@PS (1:100) PS 5：1 3.86 29 -6%~10% Example 12 GR@PS (3:100) PS 2：1 4.11 33 -7%~7% Example 13 GR@PS (5:100) PS 2：1 3.89 30 -7%~8% Example 14 GR@PS (1:100) PMMA 2：1 4.05 33 -8%~9% Example 15 GR@PS (1:100) PP 2：1 4.12 30 -8%~7% Example 16 GR@PS (1:100) PET 2：1 4.19 35 -3%~10% Example 4 GR@PMMA PMMA 2：1 4.05 30 -5%~8% Example 5 GR@PP PP 2：1 3.87 39 -10%~10% Example 6 GR@PET PET 2：1 3.44 40 -9%~9% Example 7 BNNS@PS PS 2：1 3.25 40 -9%~8% Example 8 <![CDATA[Ti3C2@PS]]> PS 2：1 3.57 37 -8%~9%

[0084] Comparing Examples 9, 2, 1, 3, 10, and 11, it can be seen that as the amount of thermally conductive filler added increases, the inter-plane thermal conductivity of the resulting composite material gradually increases, but its tensile strength gradually decreases. Considering its overall performance, Examples 1-3 are relatively excellent, with Example 2 being the most effective. Furthermore, the volatility of the composite material obtained by the present invention (here, the volatility of the tailored inter-plane thermal conductivity) is only between -10% and 10%, preferably between -7% and 8%, and more preferably between -5% and 5%. Its performance is very stable and meets the requirements for mass production.

[0085] Comparing Example 1, Example 12 and Example 13, it can be seen that as the amount of thermal conductive material added increases, the inter-surface thermal conductivity of the obtained composite material decreases, the mechanical properties decrease, and the volatility is higher.

[0086] By comparing Example 1, Example 14, Example 15, and Example 16, it can be seen that the order of their inter-surface thermal conductivity coefficients is as follows: Example 1 > Example 16 > Example 15 > Example 14, that is, Example 1 has the best performance. This is mainly because the composition of the polymer particles and the matrix is ​​the same, which reduces the interfacial thermal resistance during the hot pressing process and greatly improves the thermal conductivity.

[0087] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A composite material with an isolation structure, characterized in that: The composite material with an isolation structure comprises: A thermoplastic polymer matrix and a heat-conducting filler filled in the thermoplastic polymer matrix; the heat-conducting filler comprises thermoplastic polymer microspheres and a heat-conducting material coating layer formed on the surface of the thermoplastic polymer microspheres through electrostatic action.

2. The composite material with an isolation structure according to claim 1, characterized in that: The thermoplastic polymer matrix comprises at least one of polystyrene PS, polymethyl methacrylate PMMA, polypropylene PP, polyethylene PE, and polyethylene terephthalate PET; And / or, the thermoplastic polymer microspheres include at least one of polystyrene microspheres, polymethyl methacrylate microspheres, polypropylene microspheres, polyethylene microspheres, and polyethylene terephthalate microspheres; And / or, the thermoplastic polymer matrix and the thermoplastic polymer microspheres have the same composition.

3. The composite material with an isolation structure according to claim 1 or 2, characterized in that: The surfaces of the thermoplastic polymer microspheres and the thermally conductive material in the thermally conductive material coating layer are respectively loaded with oppositely charged groups; preferably, the surfaces of the thermoplastic polymer microspheres are loaded with positively charged groups, and the surfaces of the thermally conductive material in the thermally conductive material coating layer are loaded with negatively charged groups; More preferably, the negatively charged groups include carboxyl (-COO-), sulfonic acid (-SO3 - ), hydroxyl (-O - ) More preferably, the positively charged group comprises a proton (H + ), dialkylamino (-NR2), alkylamino (-NHR), amino (-NH2), and at least one of an organic phosphorus group.

4. The composite material with an isolation structure according to any one of claims 1 to 3, characterized in that: The mass ratio of the thermal conductive material coating layer to the thermoplastic polymer microspheres is 1:(5-100).

5. The composite material with an isolation structure according to any one of claims 1 to 4, characterized in that: The mass ratio of the thermoplastic polymer matrix to the thermal conductive filler is (1-20):1, preferably (1-3):

1.

6. The composite material with an isolation structure according to any one of claims 1 to 5, characterized in that: The particle size of the thermoplastic polymer microspheres is 1 μm to 100 μm. Preferably, the thermoplastic polymer microspheres have a hollow structure, and the wall thickness of the thermoplastic polymer microspheres is at least 5%, preferably 10% to 50%, of the particle size of the thermoplastic polymer microspheres.

7. The composite material with an isolation structure according to any one of claims 1 to 6, characterized in that: The thermally conductive material in the thermally conductive material coating layer is a two-dimensional thermally conductive material, preferably selected from at least one of graphene, graphite nanosheets, hexagonal boron nitride nanosheets, boron nitride nanotubes, two-dimensional transition metal carbides, two-dimensional transition metal nitrides, two-dimensional transition metal carbonitrides, single-walled carbon nanotubes, and multi-walled carbon nanotubes.

8. A method for preparing a composite material with an isolation structure according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) Dispersing thermoplastic polymer microspheres and thermal conductive materials respectively loaded with oppositely charged groups on their surfaces in an organic solvent free of charge aggregation and drying them to obtain a thermal conductive filler; preferably, the surfaces of the thermoplastic polymer microspheres are loaded with positively charged groups, and the surface of the thermal conductive material is loaded with negatively charged groups; (2) The thermal conductive filler and the optional thermoplastic polymer matrix are mixed and then subjected to hot pressing to obtain a composite material with an isolation structure.

9. The preparation method according to claim 8, wherein In step (2), the parameters of the hot pressing treatment include: pressure of 2.08 MPa to 10.4 MPa, temperature of 100 to 150°C, and time of 30 to 90 min.

10. Use of the composite material with an isolation structure according to any one of claims 1 to 7 in the field of heat conduction.

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