An insulating composite material containing a bamboo forest-like heat-conducting network and a preparation method thereof

Abstract

The invention discloses an insulating composite material containing a bamboo forest-like heat-conducting network, comprising the following raw materials by mass: 100 parts of an organic silicon matrix, 6-24 parts of modified spherical nano-alumina, 10-40 parts of modified carbon fibers, 1-3 parts of waterborne polyurethane, and 1-1.5 parts of an isocyanate-terminated polyurethane prepolymer. The invention also discloses a method for preparing an insulating composite material containing a bamboo forest-like heat-conducting network. In the invention, a bamboo forest-like heat-conducting network structure composed of vertically oriented modified carbon fibers and laminated bamboo leaf-shaped transversely modified nano-alumina can be formed, and a carbon fiber-filled polymer-based composite material with an out-of-plane thermal conductivity of more than 16 W / (m K) can be obtained at a relatively low (~15 vol%) content of the heat-conducting structure.

Description

Technical Field

[0001] The invention relates to the field of insulating composite materials, and in particular to an insulating composite material containing a bamboo forest-like heat-conducting network and a preparation method thereof. Background Art

[0002] Usually, elastic materials with high thermal conductivity in the vertical direction are introduced into the interface between electronic components and heat sinks to fill the interface gaps, reduce the interface thermal resistance, and improve the heat dissipation capacity of the chip. Such materials are called thermal interface materials. In modern electronic devices, chip-level thermal management requires that the thermal interface material have both high out-of-plane thermal conductivity and high resistivity to achieve efficient heat dissipation of the chip while reducing the risk of leakage.

[0003] Composite materials obtained by compounding high thermal conductivity mesophase asphalt-based carbon fibers with silicone rubber have been widely used to fill the interface between electronic components and heat sinks, achieving efficient heat dissipation in the vertical direction. However, carbon fibers have high electrical conductivity while also having high thermal conductivity. Therefore, most carbon fiber-filled polymer-based composite materials also exhibit high electrical conductivity, which greatly increases the risk of leakage of electronic components. In order to solve this problem, researchers have explored ways to improve the insulation properties of materials while maintaining the thermal conductivity of thermal interface materials. Patent No. ZL202111423859.X provides an insulating thermally conductive gasket containing COF-coated carbon fibers and a preparation method thereof. By coating the surface of the conductive carbon fibers with a covalent organic framework material COF as an insulating coating and inducing orientation, an excellent thermal conductivity of 28.6W / (m·K) can be achieved in the orientation direction of the carbon fibers. However, the volume resistivity is still not enough to meet the insulation requirements of the material. Yu Jinhong and others from the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, coated a layer of SiC on the surface of CF by chemical vapor deposition and mixed it with PDMS to prepare a new core-shell structure of CF@SiC filler and a high thermal conductivity and electrical insulation TIM. The thermal conductivity of the PDMS composite material containing 55wt% CF@SiC filler reached 4.0W / (m·K), which is 2402% higher than that of pure PDMS (0.16W / (m·K)), and the volume resistivity is 15.1Ω·cm. Carbon fiber-filled polymer-based composites can obtain high inter-plane thermal conductivity at low carbon fiber filling, but their insulation performance still needs to be improved.

[0004] At present, there is an urgent need to develop polymer-based thermally conductive composite materials with excellent insulation properties to meet the demand of the rapidly developing chip industry for high-performance thermal interface materials to ensure efficient thermal management of electronic equipment. While ensuring the safe operation of the equipment, it can also provide support for the miniaturization and high performance of electronic components, so as to promote the further development of chip thermal management material science and engineering technology. Summary of the invention

[0005] The purpose of the invention is to provide an insulating composite material containing a bamboo forest-like heat-conducting network.

[0006] The invention also provides a method for preparing an insulating composite material containing a bamboo forest-like heat-conducting network.

[0007] The innovation of the present invention lies in that a bamboo forest-like thermal conductive network structure composed of vertically oriented modified carbon fibers and stacked bamboo leaf-shaped transversely modified nano-alumina can be formed in the present invention, and a carbon fiber-filled polymer-based composite material with an out-of-plane thermal conductivity of more than 16 W / (m K) can be obtained at a relatively low (~15 vol%) content of the thermal conductive structure.

[0008] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is:

[0009] An insulating composite material containing a bamboo forest-like heat-conducting network comprises the following raw materials by mass: 100 parts of an organic silicon matrix, 6-24 parts of modified spherical nano-alumina, 10-40 parts of modified carbon fibers, 1-3 parts of waterborne polyurethane, and 1-1.5 parts of isocyanate-terminated polyurethane prepolymer.

[0010] Furthermore, the organic silicon matrix comprises hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst, and the mass ratio of hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst is 50:60:0.5~1.

[0011] Furthermore, the modified spherical nano-alumina is modified with a surface modifier, and the surface modifier is KH-540 or KH-550.

[0012] Furthermore, the waterborne polyurethane is an anionic waterborne polyurethane, and the anionic waterborne polyurethane is a carboxylic acid waterborne polyurethane containing a carboxyl-containing hydrophilic chain extender or a sulfonic acid waterborne polyurethane containing a sulfonic acid ion.

[0013] Furthermore, the modified carbon fiber is surface-coated and modified by a dopamine hydrochloride solution with a concentration of 1-2.5 mg / mL at room temperature; the carbon fiber has a diameter of 6-10 μm and a length of 150-250 μm; and the thickness of the polydopamine insulating layer on the surface of the modified carbon fiber is 30-40 nm.

[0014] Furthermore, the isocyanate-terminated polyurethane prepolymer is prepared from diisocyanate, polyether polyol and a catalyst under reaction conditions of 70° C., the molar ratio of diisocyanate to polyether polyol is 1.2-1.5:1; the catalyst is a triethylenediamine metal alkyl compound, and the content thereof is 0.1-0.3% of the mass of the diisocyanate.

[0015] Furthermore, the diisocyanate is toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) or isophorone diisocyanate (IPDI); and the polyether polyol is polyethylene glycol (PEG) or polypropylene glycol (PPG).

[0016] A method for preparing an insulating composite material containing a bamboo forest-like heat-conducting network comprises the following steps:

[0017] (1) According to the formula, the modified spherical nano-alumina, the modified carbon fiber, and the water-based polyurethane are uniformly mixed in water, the mass ratio of the modified spherical nano-alumina, the modified carbon fiber, the water-based polyurethane and the water is 6-24:10-40:1-3:100, and after directional freezing and vacuum freeze drying, a bamboo forest-like thermal conductive network structure material is obtained;

[0018] (2) according to the formula, an isocyanate-terminated polyurethane prepolymer is placed in a polar solution to obtain an isocyanate-terminated polyurethane prepolymer solution; the mass ratio of the isocyanate-terminated polyurethane prepolymer to the polar solution is 1:100-200;

[0019] (3) placing the bamboo forest-like thermal conductive network structure material in an isocyanate-terminated polyurethane prepolymer solution, using vacuum impregnation to allow the isocyanate-terminated polyurethane prepolymer to fully enter the bamboo forest-like thermal conductive network structure, and after heating, washing, and drying, coating the surface of the bamboo forest-like thermal conductive network structure material with a polymer insulating layer to obtain a pre-finished product;

[0020] (4) The pre-finished product is immersed in a silicone matrix and cured by heating to obtain a finished product.

[0021] Furthermore, the skeleton surface of the bamboo forest-like heat-conducting network structure material is coated with a polymer insulation layer with a thickness of 10 to 15 nm.

[0022] Furthermore, the temperature required for directional freezing in step (1) is -150°C, the vacuum degree during vacuum freeze drying is 30-60 Pa, and the freeze drying temperature is -50--30°C; the polar solvent in step (2) is N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAC); the heating temperature during heating, washing and drying in step (3) is 50-70°C, ethanol is used for washing 3-5 times, and the drying temperature is 60-80°C; the temperature during heating and curing in step (4) is 130-150°C, and the heating time is 1-3 hours.

[0023] The beneficial effects of the present invention are:

[0024] 1. The present invention can form a bamboo forest-like thermal conductive network structure composed of vertically oriented modified carbon fibers and laminated bamboo leaf-shaped transversely modified nano-alumina, and a carbon fiber-filled polymer-based composite material with an out-of-plane thermal conductivity of more than 16 W / (m K) can be obtained at a relatively low (~15 vol%) content of the thermal conductive structure.

[0025] 2. The polydopamine layer on the surface of the modified carbon fiber in the present invention can improve the insulation of the carbon fiber. The sheet structure formed by the bonding of nano-alumina particles isolates the modified carbon fibers from each other, further blocking the electron transfer path formed by the overlapping of the carbon fibers, and giving the composite material a higher resistivity.

[0026] 3. The waterborne polyurethane in the present invention achieves close adhesion between the modified carbon fiber and the modified nano-alumina, reducing the interfacial thermal resistance of heat conduction; the isocyanate-terminated polyurethane prepolymer can further react with the hydroxyl, amino and other functional groups on the surface of the modified carbon fiber and the modified nano-alumina, further strengthening the surface insulation layer of the modified spherical nano-alumina and the modified carbon fiber, and further improving the volume resistivity of the polymer composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the present invention.

[0028] Figure 2 This is a SEM scan of the thermal conductivity network imitating bamboo forest.

[0029] Figure 3 This is the SEM scan of carbon fiber.

[0030] Figure 4 This is the SEM scan of the modified carbon fiber. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings.

[0032] Embodiment 1: An insulating composite material containing a bamboo forest-like thermal conductive network comprises the following raw materials by mass: 100 parts of an organosilicon matrix, 6 parts of modified spherical nano-alumina, 10 parts of modified carbon fibers, 1 part of waterborne polyurethane, and 1 part of an isocyanate-terminated polyurethane prepolymer.

[0033] The organic silicon matrix comprises hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst, and the mass ratio of hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst is 50:60:0.5.

[0034] The modified spherical nano-alumina is modified with a surface modifier, and the surface modifier is KH-540.

[0035] The waterborne polyurethane is an anionic waterborne polyurethane, and the anionic waterborne polyurethane is a carboxylic acid waterborne polyurethane containing a hydrophilic chain extender containing a carboxyl group.

[0036] The modified carbon fiber is surface-coated and modified with a dopamine hydrochloride solution having a concentration of 1 mg / mL at room temperature; the carbon fiber has a diameter of 6 μm and a length of 150 μm; and the thickness of the polydopamine insulating layer on the surface of the modified carbon fiber is 30 nm.

[0037] The isocyanate-terminated polyurethane prepolymer is prepared from diisocyanate, polyether polyol and a catalyst under reaction conditions of 70° C. The molar ratio of diisocyanate to polyether polyol is 1.2:1. The catalyst is a triethylenediamine metal alkyl compound, and the content thereof is 0.1% of the mass of the diisocyanate.

[0038] The diisocyanate is toluene diisocyanate (TDI); the polyether polyol is polyethylene glycol (PEG).

[0039] Example 2: An insulating composite material containing a bamboo forest-like thermal conductive network comprises the following raw materials by mass: 100 parts of an organosilicon matrix, 12 parts of modified spherical nano-alumina, 20 parts of modified carbon fibers, 2 parts of waterborne polyurethane, and 1.2 parts of an isocyanate-terminated polyurethane prepolymer.

[0040] The organic silicon matrix comprises hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst, and the mass ratio of hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst is 50:60:0.8.

[0041] The modified spherical nano-alumina is modified with a surface modifier, and the surface modifier is KH-550.

[0042] The waterborne polyurethane is an anionic waterborne polyurethane, and the anionic waterborne polyurethane is a sulfonic acid waterborne polyurethane containing sulfonic acid ions.

[0043] The modified carbon fiber is surface-coated and modified by a dopamine hydrochloride solution with a concentration of 1.2 mg / mL at room temperature; the carbon fiber has a diameter of 8 μm and a length of 200 μm; and the thickness of the polydopamine insulating layer on the surface of the modified carbon fiber is 35 nm.

[0044] The isocyanate-terminated polyurethane prepolymer is prepared from diisocyanate, polyether polyol and a catalyst under reaction conditions of 70° C. The molar ratio of diisocyanate to polyether polyol is 1.3:1. The catalyst is a triethylenediamine metal alkyl compound, and the content thereof is 0.2% of the mass of the diisocyanate.

[0045] The diisocyanate is diphenylmethane diisocyanate (MDI); and the polyether polyol is polypropylene glycol (PPG).

[0046] Example 3: An insulating composite material containing a bamboo forest-like thermal conductive network comprises the following raw materials by mass: 100 parts of an organosilicon matrix, 24 parts of modified spherical nano-alumina, 40 parts of modified carbon fibers, 3 parts of waterborne polyurethane, and 1.5 parts of an isocyanate-terminated polyurethane prepolymer.

[0047] The organic silicon matrix comprises hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst, and the mass ratio of hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst is 50:60:1.

[0048] The modified spherical nano-alumina is modified with a surface modifier, and the surface modifier is KH-540.

[0049] The waterborne polyurethane is an anionic waterborne polyurethane, and the anionic waterborne polyurethane is a carboxylic acid waterborne polyurethane containing a hydrophilic chain extender containing a carboxyl group.

[0050] The modified carbon fiber is surface-coated and modified by a dopamine hydrochloride solution with a concentration of 2.5 mg / mL at room temperature; the carbon fiber has a diameter of 10 μm and a length of 250 μm; and the thickness of the polydopamine insulating layer on the surface of the modified carbon fiber is 40 nm.

[0051] The isocyanate-terminated polyurethane prepolymer is prepared from diisocyanate, polyether polyol and a catalyst under reaction conditions of 70° C. The molar ratio of diisocyanate to polyether polyol is 1.5:1. The catalyst is a triethylenediamine metal alkyl compound, and the content thereof is 0.3% of the mass of the diisocyanate.

[0052] The diisocyanate is isophorone diisocyanate (IPDI); and the polyether polyol is polyethylene glycol (PEG).

[0053] Embodiment 4: A method for preparing an insulating composite material containing a bamboo forest-like thermal conductive network, comprising the following steps:

[0054] (1) According to the formula of Example 1, the modified spherical nano-alumina, the modified carbon fiber, and the water-based polyurethane are uniformly mixed in water, the mass ratio of the modified spherical nano-alumina, the modified carbon fiber, the water-based polyurethane and the water is 6:10:1:100, and after directional freezing and vacuum freeze drying, a bamboo forest-like thermal conductive network structure material is obtained; the temperature required for directional freezing is -150°C, the vacuum degree during vacuum freeze drying is 30Pa, and the freeze drying temperature is -50°C;

[0055] (2) according to the formula of Example 1, an isocyanate-terminated polyurethane prepolymer is placed in a polar solution to obtain an isocyanate-terminated polyurethane prepolymer solution; the polar solvent is N,N-dimethylformamide (DMF); the mass ratio of the isocyanate-terminated polyurethane prepolymer to the polar solution is 1:100;

[0056] (3) placing the bamboo forest thermal conductive network structure material in an isocyanate-terminated polyurethane prepolymer solution, using vacuum impregnation to allow the isocyanate-terminated polyurethane prepolymer to fully enter the bamboo forest thermal conductive network structure, and after heating, washing, and drying, coating the surface of the skeleton of the bamboo forest thermal conductive network structure material with a polymer insulating layer to obtain a pre-finished product; the surface of the skeleton of the bamboo forest thermal conductive network structure material coated with a polymer insulating layer has a thickness of 10 nm; the heating temperature during heating, washing, and drying is 50° C., washing is performed with ethanol for 3 times, and the drying temperature is 60° C.;

[0057] (4) The pre-finished product is immersed in a silicone matrix and cured by heating to obtain a finished product; the temperature during the heating and curing is 130° C. and the heating time is 1 hour.

[0058] Embodiment 5: A method for preparing an insulating composite material containing a bamboo forest-like thermal conductive network, comprising the following steps:

[0059] (1) According to the formula of Example 2, the modified spherical nano-alumina, the modified carbon fiber, and the water-based polyurethane are uniformly mixed in water, the mass ratio of the modified spherical nano-alumina, the modified carbon fiber, the water-based polyurethane and the water is 12:20:2:100, and after directional freezing and vacuum freeze drying, a bamboo forest-like thermal conductive network structure material is obtained; the temperature required for directional freezing is -150°C, the vacuum degree during vacuum freeze drying is 40Pa, and the freeze drying temperature is -40°C;

[0060] (2) according to the formula of Example 2, an isocyanate-terminated polyurethane prepolymer is placed in a polar solution to obtain an isocyanate-terminated polyurethane prepolymer solution; the polar solvent is N,N-dimethylacetamide (DMAC); the mass ratio of the isocyanate-terminated polyurethane prepolymer to the polar solution is 1:150;

[0061] (3) placing the bamboo forest thermal conductive network structure material in an isocyanate-terminated polyurethane prepolymer solution, using vacuum impregnation to allow the isocyanate-terminated polyurethane prepolymer to fully enter the bamboo forest thermal conductive network structure, and after heating, washing, and drying, coating the surface of the skeleton of the bamboo forest thermal conductive network structure material with a polymer insulating layer to obtain a pre-finished product; the surface of the skeleton of the bamboo forest thermal conductive network structure material coated with a polymer insulating layer has a thickness of 12 nm; the heating temperature during heating, washing, and drying is 60° C., ethanol is used for washing 4 times, and the drying temperature is 70° C.;

[0062] (4) The pre-finished product is immersed in a silicone matrix and cured by heating to obtain a finished product; the temperature during the heating and curing is 140° C. and the heating time is 2 hours.

[0063] Embodiment 6: A method for preparing an insulating composite material containing a bamboo forest-like thermal conductive network, comprising the following steps:

[0064] (1) According to the formula of Example 3, the modified spherical nano-alumina, the modified carbon fiber, and the water-based polyurethane are uniformly mixed in water, and the mass ratio of the modified spherical nano-alumina, the modified carbon fiber, the water-based polyurethane and the water is 24:40:3:100. After directional freezing and vacuum freeze drying, a bamboo forest-like thermal conductive network structure material is obtained; the temperature required for directional freezing is -150°C, the vacuum degree during vacuum freeze drying is 60Pa, and the freeze drying temperature is -30°C;

[0065] (2) according to the formula of Example 3, an isocyanate-terminated polyurethane prepolymer is placed in a polar solution to obtain an isocyanate-terminated polyurethane prepolymer solution; the polar solvent is N,N-dimethylformamide (DMF); the mass ratio of the isocyanate-terminated polyurethane prepolymer to the polar solution is 1:200;

[0066] (3) placing the bamboo forest thermal conductive network structure material in an isocyanate-terminated polyurethane prepolymer solution, using vacuum impregnation to allow the isocyanate-terminated polyurethane prepolymer to fully enter the bamboo forest thermal conductive network structure, and after heating, washing, and drying, coating the surface of the skeleton of the bamboo forest thermal conductive network structure material with a polymer insulating layer to obtain a pre-finished product; the surface of the skeleton of the bamboo forest thermal conductive network structure material coated with a polymer insulating layer has a thickness of 15 nm; the heating temperature during heating, washing, and drying is 70° C., washing is performed with ethanol for 5 times, and the drying temperature is 80° C.;

[0067] (4) The pre-finished product is immersed in a silicone matrix and cured by heating to obtain a finished product; the temperature during the heating and curing is 150° C. and the heating time is 3 hours.

[0068] Comparative Example 1: Referring to Example 6, the modified spherical nano-alumina in the raw material was eliminated, and only the modified carbon fiber and water-based polyurethane were uniformly mixed in water.

[0069] Comparative Example 2: Referring to Example 6, the modified carbon fiber in the raw material is replaced with carbon fiber.

[0070] Comparative Example 3: Referring to Example 6, steps (2) and (3) are omitted, and the bamboo forest-like thermal conductive network structure material is immersed in a silicone matrix and heated and cured.

[0071] sample Out-of-plane thermal conductivity (W / (m K)) Volume resistivity (Ω·cm) sample Out-of-plane thermal conductivity (W / (m K)) Volume resistivity (Ω·cm) Example 4 2.1 <![CDATA[5×10 9 ]]> Comparative Example 1 7.3 <![CDATA[4×10 8 ]]> Example 5 3.0 <![CDATA[6×10 9 ]]> Comparative Example 2 8.4 <![CDATA[2×10 8 ]]> Example 6 16.3 <![CDATA[8×10 9 ]]> Comparative Example 3 14.2 <![CDATA[6×10 8 ]]>

[0072] As can be seen from Table 1, comparing Examples 4 to 6 with Comparative Examples 1 to 3: the bamboo forest-like thermal conductive network structure can transfer heat more effectively than a simply oriented carbon fiber skeleton, so the excellent thermal conductivity of the composite material can be achieved at a lower content; the polydopamine insulating layer on the surface of the carbon fiber and the alumina particle sheets between the carbon fibers can separate the carbon fibers, and at the same time, the water-based polyurethane achieves a tight bond between the modified carbon fiber and the modified spherical nano-alumina, thereby reducing the interfacial thermal resistance of heat conduction; the isocyanate-terminated polyurethane prepolymer can further react with functional groups such as hydroxyl and amino groups on the surface of the modified carbon fiber and the modified nano-alumina, strengthen the surface insulating layer of the modified nano-alumina and the modified carbon fiber, and increase the thickness of the insulating layer, thereby further blocking the electron transfer path, so that the composite material maintains the electrical insulation performance of the insulator level while achieving high thermal conductivity.

[0073] The described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. An insulating composite material containing a bamboo forest-like thermal conductive network, characterized in that: The raw materials include the following components by weight: 100 parts of organic silicon matrix, 6-24 parts of modified spherical nano-alumina, 10-40 parts of modified carbon fiber, 1-3 parts of waterborne polyurethane, and 1-1.5 parts of isocyanate-terminated polyurethane prepolymer; The modified carbon fiber is surface-coated and modified by a dopamine hydrochloride solution having a concentration of 1 to 2.5 mg / mL at room temperature; the carbon fiber has a diameter of 6 to 10 μm and a length of 150 to 250 μm; The thickness of the polydopamine insulating layer on the surface of the modified carbon fiber is 30-40 nm.

2. The insulating composite material containing the bamboo forest-like thermal conductive network according to claim 1, characterized in that: The organic silicon matrix comprises hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst, and the mass ratio of hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst is 50:60:0.5-1.

3. The insulating composite material containing the bamboo forest-like thermal conductive network according to claim 1, characterized in that: The modified spherical nano-alumina is modified by using a surface modifier, and the surface modifier is KH-540 or KH-550.

4. The insulating composite material containing a bamboo forest-like thermal conductive network according to claim 1, characterized in that: The waterborne polyurethane is an anionic waterborne polyurethane, and the anionic waterborne polyurethane is a carboxylic acid waterborne polyurethane containing a carboxyl-containing hydrophilic chain extender or a sulfonic acid waterborne polyurethane containing a sulfonic acid ion.

5. The insulating composite material containing a bamboo forest-like thermal conductive network according to claim 1, characterized in that: The isocyanate-terminated polyurethane prepolymer is prepared from diisocyanate, polyether polyol and a catalyst under reaction conditions of 70° C. The molar ratio of diisocyanate to polyether polyol is 1.2-1.5:

1. The catalyst is a triethylenediamine metal alkyl compound, and the content thereof is 0.1-0.3% of the mass of the diisocyanate.

6. The insulating composite material containing the bamboo forest-like heat-conducting network according to claim 5, characterized in that: The diisocyanate is toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) or isophorone diisocyanate (IPDI); the polyether polyol is polyethylene glycol (PEG) or polypropylene glycol (PPG).

7. A method for preparing the insulating composite material containing the bamboo forest-like thermal conductive network according to claim 1, characterized in that: The following steps are involved: (1) According to the formula, the modified spherical nano-alumina, the modified carbon fiber, and the waterborne polyurethane are uniformly mixed in water, and the mass ratio of the modified spherical nano-alumina, the modified carbon fiber, the waterborne polyurethane and the water is 6-24:10-40:1-3:

100. After directional freezing and vacuum freeze drying, a bamboo forest-like thermal conductive network structure material is obtained; (2) According to the formula, an isocyanate-terminated polyurethane prepolymer is placed in a polar solution to obtain an isocyanate-terminated polyurethane prepolymer solution; the isocyanate-terminated polyurethane prepolymer is prepared by mixing the modified spherical nano-alumina, the modified carbon fiber, the waterborne polyurethane and the water in a mass ratio of 6-24:10-40:1-3:

100. After directional freezing and vacuum freeze drying, a bamboo forest-like thermal conductive network structure material is obtained; The mass ratio of the polyurethane prepolymer to the polar solution is 1:100-200; (3) placing the bamboo forest-like thermal conductive network structure material in the isocyanate-terminated polyurethane prepolymer solution, using vacuum impregnation to allow the isocyanate-terminated polyurethane prepolymer to fully enter the bamboo forest-like thermal conductive network structure, and after heating, washing, and drying, a polymer insulating layer is coated on the skeleton surface of the bamboo forest-like thermal conductive network structure material to obtain a pre-finished product; (4) impregnating the pre-finished product in a silicone matrix, and obtaining a finished product by heating and curing.

8. The method for preparing the insulating composite material containing the bamboo forest-like thermal conductive network according to claim 7, characterized in that: The surface of the skeleton of the bamboo forest-like heat-conducting network structure material is coated with a polymer insulating layer with a thickness of 10 to 15 nm.

9. The method for preparing the insulating composite material containing the bamboo forest-like thermal conductive network according to claim 7, characterized in that: The temperature required for directional freezing in step (1) is -150°C, the vacuum degree during vacuum freeze drying is 30-60 Pa, and the freeze drying temperature is -50--30°C; the polar solution in step (2) is N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAC); the heating temperature during heating, washing and drying in step (3) is 50-70°C, ethanol is used for washing 3-5 times, and the drying temperature is 60-80°C; the temperature during heating and curing in step (4) is 130-150°C, and the heating time is 1-3 hours.

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