Lightweight heat-conducting engineering plastic and preparation method thereof

Abstract

The application relates to the technical field of high polymer composite materials, and discloses a light-weight heat-conducting engineering plastic and a preparation method thereof, which is prepared through melt blending of a polyamide resin matrix, boron-nitrogen alkane-polydimethylsiloxane hybrid polymer and a heat-conducting filler composed of a core-shell structure of graphene-liquid metal and composite ceramic microspheres with in-situ grown aluminum oxide nanowires on the surface. First, an interface compatibilizer is synthesized through nucleophilic substitution polycondensation; then, the core-shell structure filler is prepared through a mechanical chemical method, and the nanowires are in-situ grown on the surface of the microspheres through polydopamine biomimetic modification and a hydrothermal-calcination method to construct a three-dimensional heat-conducting network; finally, the light-weight heat-conducting engineering plastic is obtained through melt blending, uniform dispersion and strong interface combination of all components are realized, the engineering plastic with the characteristics of high heat-conducting coefficient, high notched impact strength and low density is obtained, and an innovative material solution is provided for fields with strict requirements on light weight and heat conduction.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a lightweight thermally conductive engineering plastic and its preparation method. Background Technology

[0002] Engineering plastics are a class of high-performance polymer materials that can maintain excellent mechanical properties, dimensional stability, heat resistance, and electrical insulation over a wide temperature range and in harsh physicochemical environments for extended periods. Examples include polyamide (PA), polycarbonate (PC), and polyphenylene sulfide (PPS). Compared to general-purpose plastics, they possess higher strength, modulus, fatigue resistance, and creep resistance, and are widely used in structural components in machinery, automobiles, and electronic and electrical industries. However, the vast majority of engineering plastics have extremely low intrinsic thermal conductivity, classifying them as insulating materials.

[0003] With the surge in power density and lightweight requirements of electronic and electrical equipment, developing specialty engineering plastics that combine excellent mechanical properties with high thermal conductivity has become a significant challenge for the industry. Current mainstream technologies improve thermal conductivity by filling with highly thermally conductive inorganic fillers (such as boron nitride and alumina), but this faces core challenges such as a substantial increase in density due to high filler content, processing difficulties, high interfacial thermal resistance, and a sharp drop in toughness. Therefore, achieving efficient construction of thermally conductive networks and a balance of mechanical properties with low filler content through innovative filler design, interfacial control, and composite processes is a key direction for the development of thermally conductive engineering plastics. Summary of the Invention

[0004] (a) Technical problems to be solved:

[0005] This invention provides a lightweight thermally conductive engineering plastic and its preparation method to solve the problems mentioned in the background art, such as low thermal conductivity of engineering plastics, large increase in density due to high filling thermally conductive filler, difficult processing, high interfacial thermal resistance and sharp drop in toughness.

[0006] (II) Technical Solution:

[0007] In a first aspect, the present invention provides a lightweight thermally conductive engineering plastic comprising the following components in parts by weight: 100 parts of polyamide resin, 2-8 parts of borazine-polysiloxane hybrid polymer, 30-50 parts of composite thermally conductive filler, 2-3 parts of lubricant, and 0.5-0.8 parts of antioxidant.

[0008] The composite thermally conductive filler comprises a core-shell structure of graphene-liquid metal and composite ceramic microspheres with nanowires grown on their surface.

[0009] Furthermore, the core of the core-shell structured graphene-liquid metal is a graphene sheet, and its shell is a continuous phase of gallium-indium alloy; the mass fraction of gallium in the gallium-indium alloy is 75%, and the mass fraction of indium is 25%.

[0010] Furthermore, the composite ceramic microspheres with nanowires grown on their surface include a carrier core microsphere and nanowires grown in situ on the surface of the carrier core microsphere; the carrier core microsphere is any one of alumina, boron nitride, and silicon carbide microspheres; and the nanowires are alumina nanowires.

[0011] Secondly, the present invention also provides a method for preparing a lightweight thermally conductive engineering plastic, comprising the following steps:

[0012] S1. Preparation of borazine-polysiloxane hybrid polymer:

[0013] Under a nitrogen atmosphere, 100 parts by weight of trichlorocycloborane, 110-120 parts by weight of triethylamine, and 200-400 parts by weight of hydroxyl-terminated polydimethylsiloxane were added to 300-500 parts by weight of tetrahydrofuran. The mixture was stirred at 20-30°C for 5-6 hours, then heated to 50-60°C and stirred for 5-10 hours. The mixture was filtered, washed with a 90% (v / v) aqueous ethanol solution, filtered again, and dried to obtain the boronane-polysiloxane hybrid polymer.

[0014] S2. Preparation of composite thermally conductive filler:

[0015] 100 parts by weight of core-shell structured graphene-liquid metal and 100-500 parts by weight of composite ceramic microspheres with nanowires grown on the surface were mixed, added to anhydrous ethanol and ultrasonically treated for 30-60 minutes, filtered and dried to obtain composite thermally conductive filler.

[0016] S3, melt blending:

[0017] Polyamide resin, borazine-polysiloxane hybrid polymer, composite thermally conductive filler, lubricant, and antioxidant are mixed evenly in a certain proportion, extruded through a twin-screw extruder, and granulated to obtain a lightweight thermally conductive engineering plastic.

[0018] Furthermore, the temperature in zones 1-5 of the S3 twin-screw extruder is 120-200℃, and the rotation speed is 60-120 r / min.

[0019] Furthermore, the preparation method of core-shell structured graphene-liquid metal is as follows: 100 parts by weight of fluorinated graphite, 90-130 parts by weight of liquid metal gallium indium alloy and 500-1000 parts by weight of isopropanol are mixed and placed in a ball mill jar for ball milling for 10-12 hours, followed by ultrasonic treatment for 2-3 hours, centrifugation to remove the supernatant, washing with isopropanol and drying to obtain core-shell structured graphene-liquid metal.

[0020] Furthermore, the preparation method of composite ceramic microspheres with nanowires grown on the surface is as follows:

[0021] Step ①: Place the carrier core microspheres in anhydrous ethanol, ultrasonically clean for 20-30 min, wash with deionized water, centrifuge 3 times, and dry to obtain clean carrier core microspheres; place the clean carrier core microspheres in a tris(hydroxymethyl)aminomethane hydrochloride buffer solution at pH 8.5, add dopamine hydrochloride while stirring continuously, continue stirring at room temperature for 12-24 h, wash with deionized water and anhydrous ethanol alternately, centrifuge 3 times, and dry to obtain polydopamine-coated microspheres.

[0022] Step 2: Add aluminum nitrate nonahydrate and urea to deionized water, stir at 40-50℃ for 20-30 min, add polydopamine-coated microspheres, stir and react at 60-90℃ for 2-4 h, wash with deionized water, centrifuge 3 times, and dry to obtain polydopamine microspheres coated with boehmite seed layer.

[0023] Step 3: Add aluminum nitrate nonahydrate and hexamethylenetetramine to deionized water, stir at 40-50℃ for 20-30 min, add polyethyleneimine, ammonia water with a concentration of 25-28wt%, and boehmite seed layer-coated polydopamine microspheres, heat to 90-110℃, let stand for 3-5 h, wash with deionized water, centrifuge 3 times, and dry to obtain boehmite nanowire-coated polydopamine microspheres.

[0024] Step 4: Calcine the polydopamine microspheres coated with boehmite nanowires in air at 500-600℃ for 1-2 hours to obtain composite ceramic microspheres with nanowires grown on the surface.

[0025] Furthermore, in step ①, the mass ratio of the clean carrier core microspheres, tris(hydroxymethyl)aminomethane hydrochloride buffer solution, and dopamine hydrochloride is 100:(1000-2000):(0.5-4).

[0026] Furthermore, in step ②, the mass ratio of aluminum nitrate nonahydrate, urea, and polydopamine-coated microspheres is (50-200):(25-100):100.

[0027] Furthermore, in step ③, the mass ratio of aluminum nitrate nonahydrate, hexamethylenetetramine, polyethyleneimine, ammonia, and boehmite seed layer coated with polydopamine microspheres is (100-500):(70-400):(0.5-5):(10-50):100.

[0028] (III) Beneficial technical effects:

[0029] This invention constructs high-performance composite materials through a three-step method: First, a borazine-polysiloxane hybrid polymer is synthesized via nucleophilic substitution polycondensation as an interfacial compatibilizer, whose BO-Si bonds can bridge different phase interfaces; second, a core-shell structured graphene-liquid metal is prepared using mechanochemical exfoliation and wetting effects, and alumina nanowires are grown in situ on the surface of ceramic microspheres through dopamine self-polymerization, urea / hexamethylenetetramine-regulated hydrothermal growth, and calcination phase transformation, and the two are combined to form a three-dimensional thermally conductive network precursor; finally, during melt blending, the compatibilizer promotes uniform dispersion of fillers and strong interfacial bonding with the polyamide matrix through molecular entanglement and interfacial interaction, while lubricants and antioxidants ensure processing stability, ultimately obtaining an engineering plastic with high thermal conductivity, excellent mechanical properties, and lightweight characteristics.

[0030] I. This invention utilizes an innovative borazane-polysiloxane hybrid polymer as a highly efficient interfacial compatibilizer. Through BO-Si covalent bridging and molecular chain entanglement, it significantly enhances the interfacial bonding between the filler and the polyamide matrix, improves stress transfer efficiency to maintain high toughness, and greatly reduces interfacial phonon scattering, laying the foundation for efficient heat transport. Simultaneously, the innovative core-shell structure of graphene-liquid metal provides ultra-high in-plane thermal conductivity and interfacial wetting bridging, forming a microscale "layered channel-three-dimensional network" dual-network interwoven structure with polydopamine-induced in-situ-grown alumina nanowire microspheres that construct a three-dimensional interpenetrating network. This multi-level heterogeneous structure greatly improves the connectivity and efficiency of the thermal conductivity pathways and produces a significant mechanical enhancement effect, thus simultaneously achieving a significant increase in thermal conductivity and excellent maintenance of comprehensive mechanical properties at a relatively low volume fraction.

[0031] Second, the engineering plastic of this invention does not sacrifice mechanical properties for improved thermal conductivity. The borazane-polysiloxane hybrid polymer interface layer, through its toughness, can effectively induce crazing in the matrix, dissipate impact energy, and prevent crack propagation along the interface under stress. Simultaneously, the three-dimensional nanowire network and dispersed graphene sheet fillers microscopically constitute numerous crack deflection, bridging, and pinning points, significantly extending the crack propagation path and consuming energy, achieving a synergistic gain in thermal conductivity and mechanical toughness.

[0032] Third, by systematically adjusting the types and proportions of the three major functional components, this invention can "customize" the performance of the final composite material as needed: it can prioritize ensuring extreme lightweight and toughness, or pursue extreme thermal conductivity. The preparation of all key functional units is completed in the precursor stage, and the final composite material molding is fully compatible with the general melt blending process, without the need to modify existing industrial production lines, paving the way for the rapid industrialization of the technology and its widespread application in fields such as electronic packaging and heat dissipation housings.

[0033] Fourth, boron and silicon in the boronazane-polysiloxane hybrid polymer of the present invention are classic flame retardant synergists. At the same time, the graphene sheet structure in the core-shell graphene-liquid metal of the present invention can form a dense carbon layer during combustion, which isolates oxygen and heat. It is expected that this material system may also have good flame retardant properties, further broadening the application prospects in harsh electronic and electrical environments. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] Liquid gallium indium alloy was prepared according to the method described in the journal "Ordnance Materials Science and Engineering", 2021, 44(06):99-103, in the article "Preparation and Thermal Conductivity Study of Liquid Gallium Indium Tin Alloy Material".

[0036] Trichlorocycloborazine was prepared according to the method described in the journal Acta Polymerica Sinica, 2021, 52(04):381-387, in the article "Synthesis and Properties of SiBCN Precursors with High Ceramic Yield Based on Cycloborazine".

[0037] The following hydroxyl-terminated polydimethylsiloxane was purchased from Jinan Guobang Chemical Co., Ltd.

[0038] Example 1:

[0039] A method for preparing a lightweight, thermally conductive engineering plastic includes the following steps:

[0040] S1. Preparation of borazine-polysiloxane hybrid polymer:

[0041] Under a nitrogen atmosphere, 100 parts by weight of trichlorocycloborane, 110 parts by weight of triethylamine, and 300 parts by weight of terminal hydroxyl polydimethylsiloxane were added to 400 parts by weight of tetrahydrofuran. The mixture was stirred at 20°C for 6 hours, then heated to 60°C and stirred for 5 hours. The mixture was filtered, washed with a 90% (v / v) aqueous ethanol solution, filtered again, and dried to obtain the boronane-polysiloxane hybrid polymer.

[0042] S2. Preparation of composite thermally conductive filler:

[0043] Step (1): Preparation of core-shell structured graphene-liquid metal:

[0044] 100 parts by weight of fluorinated graphite, 110 parts by weight of liquid metal gallium indium alloy and 800 parts by weight of isopropanol were mixed and placed in a ball mill jar and ball-milled for 10 hours. Then, the mixture was ultrasonically treated for 2 hours, the supernatant was removed by centrifugation, and the mixture was washed with isopropanol and dried to obtain a core-shell structured graphene-liquid metal.

[0045] Step (2): Preparation of composite ceramic microspheres with nanowires grown on the surface:

[0046] ① Place 100 parts by weight of alumina microspheres in 800 parts by weight of anhydrous ethanol, ultrasonically clean for 20 min, wash with deionized water, centrifuge 3 times, and dry to obtain clean alumina microspheres; Place 100 parts by weight of clean alumina microspheres in 1500 parts by weight of tris(hydroxymethyl)aminomethane hydrochloride buffer solution with pH 8.5, add 2 parts by weight of dopamine hydrochloride under continuous stirring, continue stirring at room temperature for 15 h, wash with deionized water and anhydrous ethanol alternately, centrifuge 3 times, and dry to obtain polydopamine-coated microspheres.

[0047] ② Add 100 parts by weight of aluminum nitrate nonahydrate and 50 parts by weight of urea to deionized water, stir at 50°C for 30 min, add 100 parts by weight of polydopamine-coated microspheres, stir and react at 90°C for 2 h, wash with deionized water, centrifuge 3 times, and dry to obtain polydopamine microspheres coated with boehmite seed layer.

[0048] ③ Add 300 parts by weight of aluminum nitrate nonahydrate and 200 parts by weight of hexamethylenetetramine to 10,000 parts by weight of deionized water, stir at 40°C for 20 min, add 2 parts by weight of polyethyleneimine, 20 parts by weight of ammonia water with a concentration of 26 wt%, and 100 parts by weight of polydopamine microspheres coated with boehmite seed layer, heat to 110°C, let stand and react for 3 h, wash with deionized water, centrifuge 3 times, and dry to obtain polydopamine microspheres coated with boehmite nanowires.

[0049] ④ The polydopamine microspheres coated with boehmite nanowires were calcined in air at 600°C for 1 hour to obtain composite ceramic microspheres with nanowires grown on the surface.

[0050] Step (3), Combining:

[0051] 100 parts by weight of core-shell structured graphene-liquid metal and 300 parts by weight of composite ceramic microspheres with nanowires grown on the surface were mixed, added to anhydrous ethanol and ultrasonically treated for 40 min, filtered and dried to obtain composite thermally conductive filler.

[0052] S3, melt blending:

[0053] 100 parts by weight of polyamide resin, 5 parts by weight of borazine-polysiloxane hybrid polymer, 40 parts by weight of composite thermally conductive filler, 2 parts by weight of lubricant calcium stearate, and 0.6 parts by weight of antioxidant 1010 were mixed evenly and extruded through a twin-screw extruder. The temperatures of each section of the screw extruder were 120℃, 150℃, 180℃, 200℃, and 190℃, and the rotation speed was 120 r / min. Granulation was then performed to obtain a lightweight thermally conductive engineering plastic.

[0054] Example 2:

[0055] A method for preparing a lightweight, thermally conductive engineering plastic includes the following steps:

[0056] S1. Preparation of borazine-polysiloxane hybrid polymer:

[0057] Under a nitrogen atmosphere, 100 parts by weight of trichlorocycloborane, 120 parts by weight of triethylamine, and 400 parts by weight of terminal hydroxyl polydimethylsiloxane were added to 300 parts by weight of tetrahydrofuran. The mixture was stirred at 30°C for 5 hours, then heated to 50°C and stirred for 10 hours. The mixture was then stirred for 4 hours, filtered, washed with a 90% (v / v) aqueous ethanol solution, filtered again, and dried to obtain the boronane-polysiloxane hybrid polymer.

[0058] S2. Preparation of composite thermally conductive filler:

[0059] Step (1): Preparation of core-shell structured graphene-liquid metal:

[0060] 100 parts by weight of fluorinated graphite, 130 parts by weight of liquid gallium indium alloy and 1000 parts by weight of isopropanol were mixed and placed in a ball mill jar and ball-milled for 12 hours. Then, the mixture was ultrasonically treated for 3 hours. The supernatant was removed by centrifugation, and the mixture was washed with isopropanol and dried to obtain graphene-liquid metal with a core-shell structure.

[0061] Step (2): Preparation of composite ceramic microspheres with nanowires grown on the surface:

[0062] ① Place 100 parts by weight of boron nitride microspheres in 800 parts by weight of anhydrous ethanol, ultrasonically clean for 30 min, wash with deionized water, centrifuge 3 times, and dry to obtain clean boron nitride microspheres; Place 100 parts by weight of clean boron nitride microspheres in 1000 parts by weight of tris(hydroxymethyl)aminomethane hydrochloride buffer solution with pH 8.5, add 0.5 parts by weight of dopamine hydrochloride while stirring continuously, continue stirring at room temperature for 12 h, wash with deionized water and anhydrous ethanol alternately, centrifuge 3 times, and dry to obtain polydopamine-coated microspheres.

[0063] ② Add 50 parts by weight of aluminum nitrate nonahydrate and 25 parts by weight of urea to deionized water, stir at 40°C for 20 min, add 100 parts by weight of polydopamine-coated microspheres, stir and react at 90°C for 3 h, wash with deionized water, centrifuge 3 times, and dry to obtain polydopamine microspheres coated with boehmite seed layer.

[0064] ③ Add 100 parts by weight of aluminum nitrate nonahydrate and 70 parts by weight of hexamethylenetetramine to 1000 parts by weight of deionized water, stir at 40°C for 30 min, add 0.5 parts by weight of polyethyleneimine, 10 parts by weight of ammonia water with a concentration of 28 wt%, and 100 parts by weight of polydopamine microspheres coated with boehmite seed layer, heat to 90°C, let stand for 5 h, wash with deionized water, centrifuge 3 times, and dry to obtain polydopamine microspheres coated with boehmite nanowires.

[0065] ④ The polydopamine microspheres coated with boehmite nanowires were calcined in air at 500°C for 2 hours to obtain composite ceramic microspheres with nanowires grown on the surface.

[0066] Step (3), Combining:

[0067] 100 parts by weight of core-shell structured graphene-liquid metal and 100 parts by weight of composite ceramic microspheres with nanowires grown on the surface were mixed, added to anhydrous ethanol and ultrasonically treated for 30 min, filtered and dried to obtain composite thermally conductive filler.

[0068] S3, melt blending:

[0069] 100 parts by weight of polyamide resin, 2 parts by weight of borazine-polysiloxane hybrid polymer, 30 parts by weight of composite thermally conductive filler, 3 parts by weight of lubricant calcium stearate, and 0.5 parts by weight of antioxidant 1010 were mixed evenly and extruded through a twin-screw extruder. The temperatures of each section of the screw extruder were 120℃, 150℃, 180℃, 200℃, and 190℃, and the rotation speed was 100 r / min. Granulation was then carried out to obtain a lightweight thermally conductive engineering plastic.

[0070] Example 3:

[0071] A method for preparing a lightweight, thermally conductive engineering plastic includes the following steps:

[0072] S1. Preparation of borazine-polysiloxane hybrid polymer:

[0073] Under a nitrogen atmosphere, 100 parts by weight of trichlorocycloborane, 110 parts by weight of triethylamine, and 200 parts by weight of hydroxyl-terminated polydimethylsiloxane were added to 500 parts by weight of tetrahydrofuran. The mixture was stirred at 20°C for 5 hours, then heated to 60°C and stirred for 8 hours. The mixture was filtered, washed with a 90% (v / v) aqueous ethanol solution, filtered again, and dried to obtain the boronane-polysiloxane hybrid polymer.

[0074] S2. Preparation of composite thermally conductive filler:

[0075] Step (1): Preparation of core-shell structured graphene-liquid metal:

[0076] 100 parts by weight of fluorinated graphite, 90 parts by weight of liquid gallium indium alloy and 500 parts by weight of isopropanol were mixed and placed in a ball mill jar and ball-milled for 10 hours. Then, the mixture was ultrasonically treated for 2 hours, centrifuged to remove the supernatant, washed with isopropanol and dried to obtain a core-shell structured graphene-liquid metal.

[0077] Step (2): Preparation of composite ceramic microspheres with nanowires grown on the surface:

[0078] ① Place 100 parts by weight of silicon carbide microspheres in 800 parts by weight of anhydrous ethanol, ultrasonically clean for 30 min, wash with deionized water, centrifuge 3 times, and dry to obtain clean silicon carbide microspheres; Place 100 parts by weight of clean silicon carbide microspheres in 2000 parts by weight of tris(hydroxymethyl)aminomethane hydrochloride buffer solution with pH 8.5, add 4 parts by weight of dopamine hydrochloride under continuous stirring, continue stirring at room temperature for 24 h, wash with deionized water and anhydrous ethanol alternately, centrifuge 3 times, and dry to obtain polydopamine-coated microspheres.

[0079] ② Add 200 parts by weight of aluminum nitrate nonahydrate and 100 parts by weight of urea to deionized water, stir at 40°C for 30 min, add 100 parts by weight of polydopamine-coated microspheres, stir and react at 60°C for 4 h, wash with deionized water, centrifuge 3 times, and dry to obtain polydopamine microspheres coated with boehmite seed layer.

[0080] ③ Add 500 parts by weight of aluminum nitrate nonahydrate and 400 parts by weight of hexamethylenetetramine to 10,000 parts by weight of deionized water, stir at 50°C for 20 min, add 5 parts by weight of polyethyleneimine, 50 parts by weight of ammonia water with a concentration of 25 wt%, and 100 parts by weight of polydopamine microspheres coated with boehmite seed layer, heat to 90°C, let stand and react for 4 h, wash with deionized water, centrifuge 3 times, and dry to obtain polydopamine microspheres coated with boehmite nanowires.

[0081] ④ The polydopamine microspheres coated with boehmite nanowires were calcined in air at 600°C for 1 hour to obtain composite ceramic microspheres with nanowires grown on the surface.

[0082] Step (3), Combining:

[0083] 100 parts by weight of core-shell structured graphene-liquid metal and 500 parts by weight of composite ceramic microspheres with nanowires grown on the surface were mixed, added to anhydrous ethanol, ultrasonically treated for 60 min, filtered, and dried to obtain composite thermally conductive filler.

[0084] S3, melt blending:

[0085] 100 parts by weight of polyamide resin, 8 parts by weight of borazine-polysiloxane hybrid polymer, 50 parts by weight of composite thermally conductive filler, 3 parts by weight of lubricant calcium stearate, and 0.8 parts by weight of antioxidant 1010 were mixed evenly and extruded through a twin-screw extruder. The temperatures of each section of the screw extruder were 120℃, 150℃, 180℃, 200℃, and 190℃, and the rotation speed was 60 r / min. Granulation was then performed to obtain a lightweight thermally conductive engineering plastic.

[0086] Comparative Example 1: The difference from Example 1 is that no borazane-polysiloxane hybrid polymer was added.

[0087] Comparative Example 2: The difference from Example 1 is that the thermally conductive filler uses only core-shell structured graphene-liquid metal, without adding nanowire composite microspheres.

[0088] Comparative Example 3: The difference from Example 1 is that the thermally conductive filler uses only nanowire composite microspheres, without the addition of core-shell structured graphene-liquid metal.

[0089] Comparative Example 4: The difference from Example 1 is that it is a physical mixture of ordinary graphene sheets and ordinary alumina microspheres.

[0090] S1. Mix 100 parts by weight of graphite and 300 parts by weight of alumina microspheres, add them to anhydrous ethanol, sonicate for 40 min, and dry to obtain graphite-alumina microspheres.

[0091] S2, melt blending:

[0092] 100 parts by weight of polyamide resin, 40 parts by weight of graphite-alumina microspheres, 3 parts by weight of calcium stearate lubricant, and 0.8 parts by weight of antioxidant 1010 were mixed evenly and then extruded through a twin-screw extruder. The temperatures of each section of the screw extruder were 120℃, 150℃, 180℃, 200℃, and 190℃, and the rotation speed was 60 r / min. Granulation was then performed to obtain engineering plastics.

[0093] Comparative Example 5: The difference from Example 1 is that only ordinary alumina microspheres were used.

[0094] S1, melt blending:

[0095] 100 parts by weight of polyamide resin, 40 parts by weight of alumina microspheres, 2 parts by weight of calcium stearate lubricant, and 0.6 parts by weight of antioxidant 1010 were mixed evenly and then extruded through a twin-screw extruder. The temperatures of each section of the screw extruder were 120℃, 150℃, 180℃, 200℃, and 190℃, and the rotation speed was 120 r / min. Granulation was then performed to obtain engineering plastics.

[0096] The engineering plastics obtained in Examples 1-3 and Comparative Examples 1-5 were processed and cut into test samples, and the following performance tests were performed:

[0097] The thermal conductivity of engineering plastics was tested using a flash thermal conductivity meter.

[0098] The density of engineering plastics was tested according to the method of GB / T 1033.1-2008.

[0099] Specific thermal conductivity is calculated based on the density and thermal conductivity values ​​obtained from the above tests to evaluate the thermal conductivity of engineering plastic samples of the same weight. Specific thermal conductivity = thermal conductivity / density.

[0100] The notched impact strength of engineering plastics shall be tested in accordance with the method of GB / T 1043.1-2008. The number of test specimens in each group shall not be less than 5, and the average value of 5 measurements shall be taken.

[0101] The tensile strength of engineering plastics shall be tested in accordance with the method of GB / T 1040.1-2018. The number of test specimens in each group shall not be less than 5, and the average value of 5 measurements shall be taken.

[0102] Table 1 Performance Test Table for Engineering Plastics

[0103]

[0104] As shown in Table 1, compared with Comparative Example 1, the engineering plastics of Examples 1-3 exhibit higher thermal conductivity, better specific thermal conductivity, and better mechanical properties. The engineering plastics of Examples 1-3 utilize borazine-polysiloxane hybrid polymers as highly efficient interfacial compatibilizers. Through BO-Si covalent bonding and molecular chain entanglement, the interfacial bonding force between the filler and the polyamide matrix is ​​significantly enhanced, improving stress transfer efficiency to maintain high toughness and significantly reducing interfacial phonon scattering, laying the foundation for efficient heat transport. Simultaneously, the core-shell structure of graphene-liquid metal provides ultra-high in-plane thermal conductivity and interfacial wetting bridging, forming a microscale "layered channel-three-dimensional network" dual-network interwoven structure with polydopamine-induced in-situ-grown alumina nanowire microspheres that construct a three-dimensional interpenetrating network. This multi-level heterogeneous structure greatly improves the connectivity and efficiency of the thermal conductivity pathways and produces a significant mechanical enhancement effect, thus simultaneously achieving a significant increase in thermal conductivity and excellent maintenance of comprehensive mechanical properties at a relatively low volume fraction.

[0105] Comparative Example 1 lacked the addition of a borazane-polysiloxane hybrid polymer, resulting in a weak interfacial bond between the filler and the matrix, with numerous interfacial defects and pores. This not only created stress concentration points leading to a sharp drop in impact toughness but also introduced extremely high interfacial thermal resistance, severely hindering phonon transinterfacial transport and being the root cause of the simultaneous deterioration of thermal conductivity and mechanical properties.

[0106] Comparative Example 2 uses a graphene-liquid metal two-dimensional sheet-like thermally conductive filler that retains only the core-shell structure, lacking the support and bridging of a three-dimensional nanowire network. The thermal conduction pathway is highly dependent on the orientation and contact of the graphene sheets, resulting in a large number of unconnected thermally conductive monomers. This leads to a tortuous and inefficient heat conduction path in the out-of-plane direction, making it impossible to construct an efficient three-dimensional heat transport network that runs through the entire material.

[0107] Comparative Example 3 uses only nanowire composite microspheres as thermal conductive filler. It relies solely on the three-dimensional nanowire network of nanowire composite microspheres and lacks the ultra-high in-plane thermal conductivity and interfacial wetting bridging provided by graphene-liquid metal with a core-shell structure. Its inherent path length and contact thermal resistance are higher than those of in-plane conduction, which limits the upper limit of thermal conductivity and prevents the breakthrough of the rate.

[0108] Comparative Example 4 uses a conventional physical blend of ordinary graphene sheets and ordinary alumina microspheres. This system lacks both chemically bonded core-shell structures and in-situ grown nanowires, and the interface remains unmodified. This system suffers from filler agglomeration, poor interfacial compatibility, and high intrinsic contact thermal resistance, leading to a superposition of interfacial and structural failures, highlighting the intrinsic limitations of traditional physical blending methods.

[0109] Comparative Example 5 uses only spherical alumina filler with low intrinsic thermal conductivity, which has extremely low thermal conductivity and poor compatibility with the matrix, making it impossible to balance thermal conductivity and mechanical properties.

[0110] The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, shall be within the protection scope of the present invention as long as they do not exceed the spirit covered by the specification.

Claims

1. A lightweight, thermally conductive, engineering plastic, characterized by, It includes the following components in parts by weight: 100 parts polyamide resin, 2-8 parts borazine-polysiloxane hybrid polymer, 30-50 parts composite thermally conductive filler, 2-3 parts lubricant, and 0.5-0.8 parts antioxidant; The composite thermally conductive filler includes a core-shell structured graphene-liquid metal and composite ceramic microspheres with nanowires grown on their surface. The borazane-polysiloxane hybrid polymer is prepared as follows: Under a nitrogen atmosphere, 100 parts by weight of trichlorocycloborane, 110-120 parts by weight of triethylamine, and 200-400 parts by weight of hydroxyl-terminated polydimethylsiloxane are added to 300-500 parts by weight of tetrahydrofuran. The mixture is stirred at 20-30°C for 5-6 hours, then heated to 50-60°C and stirred for 5-10 hours. The mixture is then filtered, washed with a 90% (v / v) ethanol aqueous solution, filtered again, and dried to obtain the borazane-polysiloxane hybrid polymer. The preparation method of the core-shell structured graphene-liquid metal is as follows: 100 parts by weight of fluorinated graphite, 90-130 parts by weight of liquid metal gallium indium alloy and 500-1000 parts by weight of isopropanol are mixed and placed in a ball mill jar for ball milling for 10-12 hours, followed by ultrasonic treatment for 2-3 hours, centrifugation to remove the supernatant, washing with isopropanol and drying to obtain the core-shell structured graphene-liquid metal; The method for preparing the composite ceramic microspheres with nanowires grown on their surface is as follows: Step ①: Place the carrier core microspheres in anhydrous ethanol, ultrasonically clean for 20-30 min, wash with deionized water, centrifuge 3 times, and dry to obtain clean carrier core microspheres; place the clean carrier core microspheres in a tris(hydroxymethyl)aminomethane hydrochloride buffer solution at pH 8.5, add dopamine hydrochloride while stirring continuously, continue stirring at room temperature for 12-24 h, wash with deionized water and anhydrous ethanol alternately, centrifuge 3 times, and dry to obtain polydopamine-coated microspheres; Step 2: Add aluminum nitrate nonahydrate and urea to deionized water, stir at 40-50℃ for 20-30 min, add polydopamine-coated microspheres, stir and react at 60-90℃ for 2-4 h, wash with deionized water and centrifuge 3 times, dry to obtain polydopamine microspheres coated with boehmite seed layer. Step 3: Add aluminum nitrate nonahydrate and hexamethylenetetramine to deionized water, stir at 40-50℃ for 20-30 min, add polyethyleneimine, ammonia water with a concentration of 25-28wt%, and boehmite seed layer coated polydopamine microspheres, heat to 90-110℃, let stand for 3-5 h, wash with deionized water, centrifuge 3 times, dry, and obtain boehmite nanowire coated polydopamine microspheres; Step 4: Calcine the polydopamine microspheres coated with boehmite nanowires in air at 500-600℃ for 1-2 hours to obtain composite ceramic microspheres with nanowires grown on the surface. The composite ceramic microspheres with nanowires grown on their surface include a carrier core microsphere and nanowires grown in situ on the surface of the carrier core microsphere; the carrier core microsphere is any one of alumina, boron nitride, and silicon carbide microspheres; the nanowires are alumina nanowires. In step ①, the mass ratio of the clean carrier core microspheres, tris(hydroxymethyl)aminomethane hydrochloride buffer solution, and dopamine hydrochloride is 100:(1000-2000):(0.5-4). In step ②, the mass ratio of aluminum nitrate hydrate, urea, and polydopamine-coated microspheres is (50-200):(25-100):100; The mass ratio of aluminum nitrate nonahydrate, hexamethylenetetramine, polyethyleneimine, ammonia, and boehmite seed layer coated with polydopamine microspheres in step ③ is (100-500):(70-400):(0.5-5):(10-50):

100.

2. The lightweight thermally conductive engineering plastic according to claim 1, characterized in that, The core of the graphene-liquid metal with a core-shell structure is a graphene sheet, and its shell is a continuous phase of gallium-indium alloy; the mass fraction of gallium in the gallium-indium alloy is 75%, and the mass fraction of indium is 25%.

3. A method for preparing a lightweight thermally conductive engineering plastic as described in any one of claims 1-2, characterized in that, Includes the following steps: Step 1: Preparation of composite thermally conductive filler: 100 parts by weight of core-shell structured graphene-liquid metal and 100-500 parts by weight of composite ceramic microspheres with nanowires grown on the surface were mixed, added to anhydrous ethanol and ultrasonically treated for 30-60 minutes, filtered and dried to obtain composite thermally conductive filler. Step 2: Melt blending: Polyamide resin, borazine-polysiloxane hybrid polymer, composite thermally conductive filler, lubricant, and antioxidant are mixed evenly in a certain proportion, extruded through a twin-screw extruder, and granulated to obtain a lightweight thermally conductive engineering plastic.

4. The method for preparing the lightweight thermally conductive engineering plastic according to claim 3, characterized in that, In step two, the temperature of zones 1-5 of the twin-screw extruder is 120-200℃, and the rotation speed is 60-120 r / min.

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