High-molecular thermal conductive plastic based on graphene modification and preparation method of high-molecular thermal conductive plastic

Abstract

The invention provides a graphene modification-based polymer thermal conductive plastic and a preparation method thereof, and belongs to the technical field of plastics. The preparation process comprises the following steps: preparing the functional modifier; functionally modifying the graphene; preparing and modifying a magnetic hybrid filler; and preparing the high-molecular heat-conducting plastic. Functional modifier modified graphene containing silane and imidazole groups is prepared through microwave reaction, interface thermal resistance is reduced, agglomeration is avoided, thermal conductivity is improved, interface bonding strength is enhanced, and mechanical properties are improved; using PSS to introduce negative charges on the surface of boron nitride to adsorb iron ions to prepare a magnetic hybrid filler, and applying a magnetic field to induce the filler to be directionally arranged, so as to improve the heat-conducting property; the fillers with different sizes are added into the nylon matrix to form a heat-conducting passage gradient, so that the high-molecular heat-conducting plastic which is low in content and high in heat conductivity and does not influence the comprehensive performance of the material is realized.

Description

Technical Field

[0001] The present invention relates to the field of plastic technology, and in particular to a graphene-modified polymer thermal conductive plastic and a preparation method thereof. Background Art

[0002] As CPU performance in electronic devices increases, heat dissipation becomes increasingly critical. Currently, aluminum alloys and other metal materials are the mainstream choice for CPU heat sinks due to their high thermal conductivity. However, metals have issues such as high density, difficult processing, and high cost, hindering the development of lightweight electronic devices.

[0003] Plastics hold great potential as a substitute for metals in heat dissipation. While plastics offer advantages such as low density, ease of processing, and low cost, their low thermal conductivity makes them inadequate for heat dissipation. Researchers have been creating thermally conductive plastics by adding traditional thermally conductive materials like metal oxides and graphite. However, due to the limited thermal conductivity of these fillers, large quantities of fillers are required, increasing processing difficulties, reducing product quality, and impairing mechanical properties.

[0004] Graphene, a novel two-dimensional carbon nanomaterial, boasts excellent thermal conductivity. Its two-dimensional structure facilitates the formation of heat conduction pathways within a polymer matrix. However, due to its large surface area and strong van der Waals forces, graphene tends to aggregate within the polymer resin matrix, making it difficult to form an effective heat conduction network. High filler content is often required to achieve the target thermal conductivity. This not only significantly increases costs due to the high cost of graphene but also affects properties such as plastic processing fluidity.

[0005] Therefore, we proposed a graphene-modified polymer thermal conductive plastic and preparation method that can solve the graphene agglomeration problem, has low content and high thermal conductivity without affecting the comprehensive performance of the material, which is of great significance for the heat dissipation of low-power CPUs. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a graphene-modified polymer thermal conductive plastic and a preparation method.

[0007] A graphene-modified polymer thermally conductive plastic comprising the following components:

[0008] 8-10 parts by weight of 20-50 μm functionalized modified graphene, 3-5 parts by weight of 1-5 μm modified magnetic hybrid filler, 100-120 parts by weight of nylon matrix resin, 2-3 parts by weight of lubricant and 0.3-0.5 parts by weight of antioxidant;

[0009] The functionalized modified graphene is composed of 10-12 parts by weight of graphite powder and 0.2-0.3 parts by weight of a functionalized modifier;

[0010] The functionalized modifier is prepared by microwave reaction of 8.2-8.5 parts by weight of N-methylimidazole and 28.8-31.2 parts by weight of 3-chloropropyltriethoxysilane;

[0011] The modified magnetic hybrid filler is prepared by pre-treating boron nitride with PSS and then dispersing it in deionized water. Then, an iron salt solution and 1,6-hexanediamine are added to react to prepare a magnetic hybrid filler. The magnetic hybrid filler is then treated with plasma fluorination and then modified with sodium ricinoleate to prepare a modified magnetic hybrid filler.

[0012] A method for preparing a graphene-modified polymer thermally conductive plastic comprises the following steps:

[0013] S1: Preparation of functionalized modifiers

[0014] First, N-methylimidazole and 3-chloropropyltriethoxysilane are subjected to microwave reaction, and after the reaction is completed, the reaction is washed and dried by rotary evaporation to obtain a functionalized modifier;

[0015] S2: Functionalized modified graphene

[0016] The functionalized modifier and graphite powder are separated into anhydrous ethanol, and then ball milled to obtain functionalized modified graphene;

[0017] S3: Preparation and modification of magnetic hybrid fillers

[0018] The ultrasonically treated boron nitride powder is added to a 10-12 wt% PSS aqueous solution, and the pH is adjusted to 3 to react to prepare a pretreated boron nitride powder. The pretreated boron nitride powder is then dispersed in deionized water, and a 7.5-8 wt% iron salt solution and 1,6-hexanediamine are added to react to obtain a magnetic hybrid filler. The magnetic hybrid filler is then treated with plasma fluorination, and the magnetic hybrid filler is modified and fluorinated with sodium ricinoleate to prepare a modified magnetic hybrid filler.

[0019] S4: Preparation of polymer thermal conductive plastics

[0020] Functionalized modified graphene, modified magnetic hybrid filler, nylon matrix resin, lubricant and antioxidant are mixed and then melt-reacted and extruded. After the melt is extruded through a die, a DC magnetic field of 0.3-0.5T perpendicular to the extrusion direction is applied to it, and heat treatment is performed at the same time. After the heat treatment, it is naturally cooled to room temperature to obtain a polymer thermal conductive plastic.

[0021] Furthermore, step S1 of preparing the functionalized modifier specifically includes the following steps:

[0022] S1.1: 8.2-8.5 parts by weight of N-methylimidazole and 28.8-31.2 parts by weight of 3-chloropropyltriethoxysilane were added to a three-necked flask and magnetically stirred at room temperature for 30-40 minutes. The mixture was then placed in a microwave reactor and microwaved at a power of 200-220 W for 20-30 seconds. The microwave treatment was stopped and stirred for 30-40 seconds. The above operation was repeated for microwave treatment for an effective microwave time of 5-6 minutes to obtain a reaction mixture.

[0023] S1.2: After the reaction mixture is cooled to room temperature, it is washed with ethyl acetate and petroleum ether 2-3 times respectively, then rotary evaporated, and finally vacuum dried at 80-82°C to obtain a functionalized modifier.

[0024] Furthermore, step S2 of functionalizing and modifying graphene specifically includes the following steps:

[0025] S2.1: Add 10-12 parts by weight of graphite powder and 0.2-0.3 parts by weight of a functional modifier to 50-60 parts by weight of anhydrous ethanol, and ultrasonically disperse for 20-30 minutes to obtain a dispersion;

[0026] S2.2: Add the dispersion into a ball mill, then add zirconium oxide grinding balls with a ball-to-material mass ratio of 10-12:1, then ball mill at 150-180 r / min for 12-14 h, wash the ball milled product with deionized water 2-3 times, then vacuum dry it at 60-65 ° C for 6-8 h, grind and sieve to obtain 20-50 μm functionalized modified graphene.

[0027] Furthermore, step S3 of preparing and modifying the magnetic hybrid filler specifically includes the following steps:

[0028] S3.1: Add 5-8 parts by weight of the ultrasonically treated boron nitride powder to 10-12 parts by weight of a 10-12 wt% PSS aqueous solution, stir and mix for 1-2 hours, then add 1M hydrochloric acid solution dropwise, adjust the pH to 3, and stir and mix again for 1-2 hours. After standing for 12-14 hours, filter, and wash the filtered precipitate with ethanol and deionized water until neutral, and then vacuum dry to obtain pretreated boron nitride powder;

[0029] S3.2: 10-12 parts by weight of pretreated boron nitride powder is added to deionized water, stirred and dispersed for 10-20 minutes to prepare a 10-12 wt% mixed suspension, then 80-90 parts by weight of a 7.5-8 wt% iron salt solution is added, stirred and mixed for 20-30 minutes, then 15-20 parts by weight of 1,6-hexanediamine is added, and the mixture is allowed to settle for 24-25 hours, then filtered, and the filtered precipitate is washed 2-3 times with ethanol and deionized water, then dried and ground to obtain a magnetic hybrid filler;

[0030] S3.3: Placing the magnetic hybrid filler in a reactor for plasma fluorination treatment, setting the voltage to 28-30 kV and the frequency to 9-10 kHz, using nitrogen and CF4 at a ratio of 25-26:1, and fluorinating for 10-15 minutes to obtain the fluorinated magnetic hybrid filler;

[0031] S3.4: Add 2-3 parts by weight of sodium ricinoleate to 10-12 parts by weight of anhydrous ethanol, then stir at 40-60°C for 20-30 minutes, then add 3-5 parts by weight of fluorinated magnetic hybrid filler, continue stirring and mixing for 2-3 hours, and after the reaction is completed, wash with anhydrous ethanol 2-3 times, filter, dry, grind and sieve to obtain a 1-5μm modified magnetic hybrid filler.

[0032] Furthermore, the iron salt solution in step S3.2 is specifically an iron salt solution containing FeCl3 and FeCl2. 2+ with Fe 3 + The molar ratio is 1:2.

[0033] Furthermore, step S4 of preparing the polymer thermal conductive plastic specifically includes the following steps:

[0034] S4.1: Place 8-10 parts by weight of functionalized modified graphene and 3-5 parts by weight of modified magnetic hybrid filler in a high-speed mixer, then add 100-120 parts by weight of nylon matrix resin, 2-3 parts by weight of lubricant, and 0.3-0.5 parts by weight of antioxidant, and start the high-speed mixer to mix to prepare a mixture;

[0035] S4.2: Adding the mixture into a twin-screw extruder barrel, performing a melt reaction and mixing at 180-300°C, extruding the melt through the twin-screw extruder barrel, applying a DC magnetic field of 0.3-0.5T perpendicular to the extrusion direction to the melt after extrusion through a die, and simultaneously performing a heat treatment. After the heat treatment, the melt is naturally cooled to room temperature to obtain a polymer thermal conductive plastic.

[0036] The heat treatment is specifically as follows: heating to 70-80°C at 2-3°C / min and keeping warm for 10-20 minutes, then heating to 110-125°C at 3-4°C / min and keeping warm for 30-45 minutes, and cooling to 40-45°C at 0.2-0.4°C / min.

[0037] Furthermore, in step S4.1, the lubricant is one or more of calcium stearate and zinc stearate.

[0038] Furthermore, the antioxidant in step S4.1 is one or more of antioxidant 264, antioxidant 1010, and antioxidant 1076.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects:

[0040] 1. The present invention prepares a functionalized modifier containing silane and imidazole groups by microwave reaction of N-methylimidazole and 3-chloropropyltriethoxysilane. Graphene is modified by the functionalized modifier. The functionalized modifier is combined with the graphene surface through chemical bonds to form a "bridge" structure, which reduces the interfacial thermal resistance between the graphene and the polymer matrix and avoids agglomeration, making heat transfer more efficient. A continuous thermal conductive network can be formed in the polymer matrix, thereby effectively improving the thermal conductivity. At the same time, the graphene modified by the functionalized modifier has a rough surface, which enhances the interfacial bonding strength between the graphene and the polymer matrix, thereby improving the mechanical properties of the thermally conductive plastic and avoiding damage to the mechanical properties caused by the addition of thermally conductive fillers.

[0041] 2. The present invention can introduce negative charges on the surface of boron nitride through PSS, and then iron ions can be adsorbed on the surface of boron nitride. PSS serves as a bridge connecting magnetic ferrite and boron nitride particles, thereby preparing boron nitride with surface-loaded ferroferric oxide particles. It is added to the polymer matrix as a functional filler to provide more contact points for the thermal conductivity path. Then, a magnetic field is applied to induce the filler to arrange in a directional manner, which can cooperate with the thermal conductivity system to form a highly ordered thermal conductivity path, further improving the thermal conductivity coefficient.

[0042] 3. The present invention fluorinates the surface of the magnetic hybrid filler in an N2 / CF4 plasma environment to introduce fluorine-containing groups, and then introduces sodium ricinoleate. The carboxylate hydrophilic end of the sodium ricinoleate can be combined with the polar sites on the surface of the fluorinated filler through ionic bonds or hydrogen bonds to form a strong organic coating layer. The hydrophobic alkyl chains in the organic coating layer of sodium ricinoleate can form a compatible structure with the polymer chains of the plastic matrix, forming a "filler-surfactant-matrix" bridging effect, further enhancing the interfacial bonding force, avoiding the debonding problem between the filler and the matrix, and helping to improve the mechanical properties of the composite material. At the same time, the long alkyl chain provides a steric hindrance effect to prevent the filler from agglomerating in the polymer, improve dispersibility, facilitate the formation of a thermal conductive path, and improve thermal conductivity. The molecular layer of sodium ricinoleate acts as a flexible interface layer to buffer the stress generated by the difference in thermal expansion coefficient between the filler and the matrix, avoid the destruction of the thermal conductive path caused by interface microcracks, and further optimize the heat conduction efficiency.

[0043] 4. The present invention adds large-sized functionalized modified graphene and small-sized modified magnetic hybrid fillers to the nylon matrix resin. The large-sized functionalized modified graphene forms the dominant heat path, and the small-sized modified magnetic hybrid filler has voids, forming a secondary network. From the large-sized functionalized modified graphene skeleton as the heat conduction trunk to the small-sized modified magnetic hybrid filler filling bridge as the heat conduction branch, and then to the matrix tightly connected by chemical bonds, a size gradient and an interface bonding strength gradient of the heat conduction path are formed. This structure maximizes the thermal conductivity of the filler, provides more and more efficient phonon transfer paths, and thus achieves a low-content high thermal conductivity effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is the reaction formula of the functionalized modifier according to the embodiment of the present invention;

[0045] Figure 2 This is a scanning electron microscope image of the functionalized modified graphene and graphene in Example 1 of the present invention. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0047] A method for preparing a graphene-modified polymer thermally conductive plastic, such as Figure 1 As shown, the following steps are included:

[0048] S1: Preparation of functionalized modifiers

[0049] S1.1: 8.2 parts by weight of N-methylimidazole and 28.8 parts by weight of 3-chloropropyltriethoxysilane were added to a three-necked flask and magnetically stirred at room temperature for 30 min. The flask was then placed in a microwave reactor and microwaved at 200 W for 20 s. The microwave treatment was stopped and stirred for 30 s. The above operation was repeated for a microwave treatment time of 5 min to obtain a reaction mixture.

[0050] S1.2: After cooling the reaction mixture to room temperature, wash it twice with ethyl acetate and petroleum ether, respectively, then perform rotary evaporation and finally dry it in a vacuum oven at 80°C to obtain a functionalized modifier;

[0051] S2: Functionalized modified graphene

[0052] S2.1: Add 10 parts by weight of graphite powder and 0.2 parts by weight of a functional modifier to 50 parts by weight of anhydrous ethanol and ultrasonically disperse for 20 minutes to obtain a dispersion;

[0053] S2.2: The dispersion was added to a ball mill, followed by zirconia grinding balls at a ball-to-material ratio of 10:1. The milled product was then ball-milled at 150 rpm for 12 h. The product was washed twice with deionized water and vacuum-dried at 60°C for 6 h. The product was ground and sieved to obtain functionalized modified graphene with a particle size of 20-50 μm.

[0054] S3: Preparation and modification of magnetic hybrid fillers

[0055] S3.1: 5 parts by weight of ultrasonically treated boron nitride powder was added to 10 parts by weight of a 10 wt% PSS aqueous solution, stirred and mixed for 1 hour, and then a 1 M hydrochloric acid solution was added dropwise to adjust the pH to 3. The mixture was stirred and mixed again for 1 hour. The mixture was allowed to stand for 12 hours and then filtered. The filtered precipitate was washed with ethanol and deionized water until neutral, and then vacuum dried to obtain a pretreated boron nitride powder.

[0056] The boron nitride powder ultrasonic treatment step comprises: preparing a 1 wt% boron nitride solution, ultrasonicating it continuously for 5 hours at an ultrasonic power of 1000 W, and drying it to obtain the ultrasonicated boron nitride powder;

[0057] S3.2: 10 parts by weight of pretreated boron nitride powder was added to deionized water and stirred for 10 minutes to prepare a 10 wt% mixed suspension. 80 parts by weight of a 7.5 wt% iron salt solution was then added and stirred for 20 minutes. 15 parts by weight of 1,6-hexanediamine was then added and allowed to settle for 24 hours. The mixture was then filtered and the filtered precipitate was washed twice with ethanol and deionized water, and then dried and ground to obtain a magnetic hybrid filler.

[0058] S3.3: Placing the magnetic hybrid filler in a reactor for plasma fluorination treatment, setting the voltage to 28 kV and the frequency to 9 kHz, using nitrogen and CF in a ratio of 25:1, and fluorinating for 10 minutes to obtain the fluorinated magnetic hybrid filler;

[0059] S3.4: Add 2 parts by weight of sodium ricinoleate to 10 parts by weight of anhydrous ethanol, then stir at 40°C for 20 minutes. Then add 3 parts by weight of the fluorinated magnetic hybrid filler, continue stirring and mixing for 2 hours. After the reaction is complete, wash twice with anhydrous ethanol, filter, dry, grind, and sieve to obtain a 1-5 μm modified magnetic hybrid filler.

[0060] The iron salt solution is specifically an iron salt solution containing FeCl3 and FeCl2. 2+ with Fe 3+ The molar ratio is 1:2;

[0061] S4: Preparation of polymer thermal conductive plastics

[0062] S4.1: 8 parts by weight of functionalized modified graphene and 3 parts by weight of modified magnetic hybrid filler are placed in a high-speed mixer, followed by 100 parts by weight of nylon matrix resin, 2 parts by weight of zinc stearate, and 0.3 parts by weight of antioxidant 264. The mixture is mixed in the high-speed mixer to prepare a mixture.

[0063] S4.2: The mixture is added into the barrel of a twin-screw extruder, and they are melt-reacted and mixed at 180°C. After the melt reaction and mixing, they are extruded from the barrel of a twin-screw extruder. After the melt is extruded through a die, a DC magnetic field of 0.3T is applied to it in a perpendicular extrusion direction. At the same time, heat treatment is performed. After heat treatment, it is naturally cooled to room temperature to obtain a polymer thermal conductive plastic.

[0064] The heat treatment was specifically as follows: heating to 70°C at 2°C / min and holding for 10 min, then heating to 110°C at 3°C / min and holding for 30 min, and then cooling to 40°C at 0.2°C / min.

[0065] Example 2

[0066] A method for preparing a graphene-modified polymer thermally conductive plastic, such as Figure 1 As shown, the following steps are included:

[0067] S1: Preparation of functionalized modifiers

[0068] S1.1: 8.5 parts by weight of N-methylimidazole and 31.2 parts by weight of 3-chloropropyltriethoxysilane were added to a three-necked flask and magnetically stirred at room temperature for 30 min. The flask was then placed in a microwave reactor and microwaved at 200 W for 20 s. The microwave treatment was stopped and stirred for 30 s. The above operation was repeated for a microwave treatment time of 5 min to obtain a reaction mixture.

[0069] S1.2: After cooling the reaction mixture to room temperature, wash it twice with ethyl acetate and petroleum ether, respectively, then rotary evaporate it, and finally dry it in a vacuum oven at 80°C to obtain a functionalized modifier;

[0070] S2: Functionalized modified graphene

[0071] S2.1: Add 12 parts by weight of graphite powder and 0.3 parts by weight of a functional modifier to 60 parts by weight of anhydrous ethanol, and ultrasonically disperse for 20 minutes to obtain a dispersion;

[0072] S2.2: The dispersion was added to a ball mill, followed by zirconia grinding balls at a ball-to-material ratio of 12:1. The milled product was then ball milled at 150 rpm for 12 h. The milled product was washed twice with deionized water and vacuum dried at 60°C for 6 h. The product was ground and sieved to obtain functionalized modified graphene with a particle size of 20-50 μm.

[0073] S3: Preparation and modification of magnetic hybrid fillers

[0074] S3.1: 8 parts by weight of ultrasonically treated boron nitride powder was added to 12 parts by weight of a 12 wt% PSS aqueous solution, stirred and mixed for 1 hour, and then a 1 M hydrochloric acid solution was added dropwise to adjust the pH to 3. The mixture was stirred and mixed again for 1 hour. The mixture was allowed to stand for 12 hours and then filtered. The filtered precipitate was washed with ethanol and deionized water until neutral, and then vacuum dried to obtain a pretreated boron nitride powder.

[0075] The boron nitride powder ultrasonic treatment step includes preparing a 2 wt% boron nitride solution, ultrasonicating the solution at an ultrasonic power of 1000 W for 5 hours, and drying the solution to obtain the ultrasonicated boron nitride powder.

[0076] S3.2: 12 parts by weight of pretreated boron nitride powder was added to deionized water and stirred for 10 minutes to prepare a 12 wt% mixed suspension. 90 parts by weight of an 8 wt% iron salt solution was then added and stirred for 20 minutes. 20 parts by weight of 1,6-hexanediamine was then added and allowed to settle for 24 hours. The mixture was then filtered and the filtered precipitate was washed twice with ethanol and deionized water, and then dried and ground to obtain a magnetic hybrid filler.

[0077] S3.3: Placing the magnetic hybrid filler in a reactor for plasma fluorination treatment, setting the voltage to 28 kV and the frequency to 9 kHz, using nitrogen and CF in a ratio of 26:1, and fluorinating for 10 minutes to obtain the fluorinated magnetic hybrid filler;

[0078] S3.4: Add 3 parts by weight of sodium ricinoleate to 12 parts by weight of anhydrous ethanol, followed by stirring at 40°C for 20 minutes. Then, add 5 parts by weight of the fluorinated magnetic hybrid filler, and continue stirring and mixing for 2 hours. After the reaction is complete, wash twice with anhydrous ethanol, filter, dry, grind, and sieve to obtain a 1-5 μm modified magnetic hybrid filler.

[0079] The iron salt solution is specifically an iron salt solution containing FeCl3 and FeCl2. 2+ with Fe 3+ The molar ratio is 1:2;

[0080] S4: Preparation of polymer thermal conductive plastics

[0081] S4.1: Place 10 parts by weight of functionalized modified graphene and 5 parts by weight of modified magnetic hybrid filler in a high-speed mixer, then add 120 parts by weight of nylon matrix resin, 3 parts by weight of calcium stearate, and 0.5 parts by weight of antioxidant 1010, and start the high-speed mixer to mix to prepare a mixture;

[0082] S4.2: The mixture is added into the barrel of a twin-screw extruder, and they are melt-reacted and mixed at 180°C. After the melt reaction and mixing, they are extruded from the barrel of a twin-screw extruder. After the melt is extruded through a die, a DC magnetic field of 0.3T is applied to it in a perpendicular extrusion direction. At the same time, heat treatment is performed. After heat treatment, it is naturally cooled to room temperature to obtain a polymer thermal conductive plastic.

[0083] The heat treatment was specifically as follows: heating to 70°C at 2°C / min and holding for 10 min, then heating to 110°C at 3°C / min and holding for 30 min, and then cooling to 40°C at 0.2°C / min.

[0084] Example 3

[0085] A method for preparing a graphene-modified polymer thermally conductive plastic, such as Figure 1 As shown, the following steps are included:

[0086] S1: Preparation of functionalized modifiers

[0087] S1.1: 8.2 parts by weight of N-methylimidazole and 28.8 parts by weight of 3-chloropropyltriethoxysilane were added to a three-necked flask and magnetically stirred at room temperature for 40 min. The mixture was then placed in a microwave reactor and microwaved at 220 W for 30 s. The microwave treatment was stopped and stirred for 40 s. The above operation was repeated for a microwave treatment time of 6 min to obtain a reaction mixture.

[0088] S1.2: After cooling the reaction mixture to room temperature, wash it three times with ethyl acetate and petroleum ether, respectively, then rotary evaporate it and finally dry it in a vacuum oven at 82°C to obtain a functionalized modifier.

[0089] S2: Functionalized modified graphene

[0090] S2.1: Add 10 parts by weight of graphite powder and 0.2 parts by weight of a functional modifier to 50 parts by weight of anhydrous ethanol and ultrasonically disperse for 30 minutes to obtain a dispersion;

[0091] S2.2: The dispersion was added to a ball mill, followed by zirconia grinding balls at a ball-to-material ratio of 10:1. The milled product was then ball-milled at 180 rpm for 14 h. The product was washed three times with deionized water and vacuum-dried at 65°C for 8 h. The product was ground and sieved to obtain functionalized modified graphene with a particle size of 20-50 μm.

[0092] S3: Preparation and modification of magnetic hybrid fillers

[0093] S3.1: 5 parts by weight of ultrasonically treated boron nitride powder was added to 10 parts by weight of a 10 wt% PSS aqueous solution, and the mixture was stirred for 2 h. 1 M hydrochloric acid solution was then added dropwise to adjust the pH to 3. The mixture was stirred again for 2 h. The mixture was allowed to stand for 14 h and then filtered. The filtered precipitate was washed with ethanol and deionized water until neutral, and then vacuum dried to obtain pretreated boron nitride powder.

[0094] The boron nitride powder ultrasonic treatment step includes preparing a 1 wt% boron nitride solution, ultrasonicating it continuously at an ultrasonic power of 1200 W for 8 hours, and drying it to obtain the ultrasonicated boron nitride powder;

[0095] S3.2: 10 parts by weight of pretreated boron nitride powder was added to deionized water and stirred for 10 minutes to prepare a 10 wt% mixed suspension. 80 parts by weight of a 7.5 wt% iron salt solution was then added and stirred for 30 minutes. 15 parts by weight of 1,6-hexanediamine was then added and allowed to settle for 25 hours. The mixture was then filtered and the filtered precipitate was washed three times with ethanol and deionized water, and then dried and ground to obtain a magnetic hybrid filler.

[0096] S3.3: Plasma fluorination treatment of the magnetic hybrid filler was performed in a reactor. The voltage was set to 30 kV and the frequency was set to 10 kHz. The gas was nitrogen and CF at a ratio of 25:1. The fluorination was continued for 15 minutes to obtain the fluorinated magnetic hybrid filler.

[0097] S3.4: Add 2 parts by weight of sodium ricinoleate to 10 parts by weight of anhydrous ethanol, then stir at 60°C for 30 minutes. Then add 3 parts by weight of the fluorinated magnetic hybrid filler, and continue stirring and mixing for 3 hours. After the reaction is complete, wash twice with anhydrous ethanol, filter, dry, grind, and sieve to obtain a 1-5 μm modified magnetic hybrid filler.

[0098] The iron salt solution is specifically an iron salt solution containing FeCl3 and FeCl2. 2+ with Fe 3+ The molar ratio is 1:2;

[0099] S4: Preparation of polymer thermal conductive plastics

[0100] S4.1: 8 parts by weight of functionalized modified graphene and 3 parts by weight of modified magnetic hybrid filler were placed in a high-speed mixer, followed by 100 parts by weight of nylon matrix resin, 2 parts by weight of zinc stearate, and 0.3 parts by weight of antioxidant 1076. The mixture was mixed in the high-speed mixer to prepare a mixture.

[0101] S4.2: The mixture is added into the barrel of a twin-screw extruder, and they are melt-reacted and mixed at 300°C. After the melt reaction and mixing, they are extruded from the barrel of a twin-screw extruder. After the melt is extruded through a die, a DC magnetic field of 0.5T is applied to it in a perpendicular extrusion direction. At the same time, heat treatment is performed. After heat treatment, it is naturally cooled to room temperature to obtain a polymer thermal conductive plastic.

[0102] The heat treatment was specifically as follows: heating to 80°C at 3°C / min and holding for 20 min, then heating to 125°C at 4°C / min and holding for 45 min, and then cooling to 45°C at 0.4°C / min.

[0103] Comparative Example 1

[0104] Compared with Example 1, the difference of Comparative Example 1 is that Comparative Example 1 removes steps S1-S2, replaces the functionalized modified graphene in step S4.1 with graphene of the same size, and prepares the polymer thermal conductive plastic without changing the other steps, which is recorded as Comparative Example 1.

[0105] Comparative Example 2

[0106] Compared with Example 1, the difference of Comparative Example 2 is that Comparative Example 2 removes steps S3.1-S3.2, replaces the magnetic hybrid filler in step S3.4 with boron nitride powder of the same size, and prepares the polymer thermal conductive plastic in the remaining steps unchanged, which is recorded as Comparative Example 2.

[0107] Comparative Example 3

[0108] Compared with Example 1, the difference of Comparative Example 3 is that the functionalized modified graphene obtained by grinding and sieving in step S2.2 has a size of 1-5 μm, and the other steps remain unchanged to prepare the polymer thermal conductive plastic, which is recorded as Comparative Example 3.

[0109] Comparative Example 4

[0110] Compared with Example 1, the difference of Comparative Example 4 is that the size of the modified magnetic hybrid filler obtained by grinding and sieving in step S3.4 is 20-50 μm, and the other steps are unchanged to prepare the polymer thermal conductive plastic, which is recorded as Comparative Example 4.

[0111] Comparative Example 5

[0112] Compared with Example 1, the difference of Comparative Example 5 is that step S3.3 is removed in Comparative Example 5, and the fluorinated magnetic hybrid filler in step S3.4 is replaced with a magnetic hybrid filler. The other steps remain unchanged to prepare the polymer thermal conductive plastic, which is recorded as Comparative Example 5.

[0113] Comparative Example 6

[0114] Compared with Example 1, the difference of Comparative Example 6 is that step S3.4 is removed in Comparative Example 6, and the modified magnetic hybrid filler in step S4.1 is replaced with a fluorinated magnetic hybrid filler. The remaining steps remain unchanged to prepare the polymer thermal conductive plastic, which is recorded as Comparative Example 6.

[0115] The thermal conductivity of the polymer thermal conductive plastics prepared in Examples 1-3 and Comparative Examples 1-4 and 6 was measured. The measurement results are shown in Table 1.

[0116] Table 1. Thermal conductivity test results

[0117] Thermal conductivity (W / k·m) Example 1 3.23 Example 2 3.18 Example 3 3.21 Comparative Example 1 2.33 Comparative Example 2 1.98 Comparative Example 3 2.02 Comparative Example 4 2.12 Comparative Example 6 2.42

[0118] As can be seen from the data in Table 1, the thermal conductivity of Comparative Example 1 is significantly lower than that of the embodiment, indicating that modifying graphene with a functional modifier can effectively improve heat transfer, thereby effectively improving thermal conductivity. As can be seen from the data in Comparative Example 2, adding the prepared modified magnetic hybrid filler to the matrix can further improve the thermal conductivity coefficient. As can be seen from the data in Comparative Examples 3-4, by adding large-sized functional modified graphene and small-sized modified magnetic hybrid fillers to the nylon matrix resin, the thermal conductivity of the filler can be maximized by the difference in size, thereby achieving a low-content, high-thermal conductivity effect. As can be seen from the data in Comparative Example 6, sodium ricinoleate modification is conducive to the formation of a thermal conductive path and improves thermal conductivity.

[0119] The mechanical properties of the polymer thermal conductive plastics prepared in Examples 1-3 and Comparative Examples 1, 5-6 were tested. The test results are shown in Table 1.

[0120] Table 2. Table 2. Mechanical properties test results

[0121] Tensile strength (MPa) Example 1 75.3 Example 2 75.9 Example 3 75.4 Comparative Example 1 59.8 Comparative Example 5 65.4 Comparative Example 6 60.2

[0122] From the data in Table 2, it can be seen that graphene modified with a functional modifier can improve the mechanical properties of the thermally conductive plastic and avoid the loss of mechanical properties caused by the addition of thermally conductive fillers. From the data in Comparative Examples 5-6, it can be seen that fluorination treatment of the magnetic hybrid filler followed by sodium ricinoleate modification can effectively improve the mechanical properties of the composite material.

[0123] Figure 2 a is a scanning electron micrograph of unmodified graphene, b is a scanning electron micrograph of functionalized modified graphene in Example 1, Figure 2 It can be seen that the unmodified graphene generally presents a smooth graphite sheet structure, while the functionalized modified graphene has a rough surface, indicating that the functionalized modified graphene can increase the contact area with the matrix resin and further improve the mechanical properties and thermal conductivity of the polymer thermal conductive plastic.

[0124] It should be understood that those skilled in the art may make improvements or modifications based on the above description, and all such improvements and modifications shall fall within the scope of protection of the appended claims. Any portion of this specification not described in detail is prior art known to those skilled in the art.

Claims

1. A graphene-modified polymer thermal conductive plastic, characterized in that: Includes the following components: 8-10 parts by weight of 20-50 μm functionalized modified graphene, 3-5 parts by weight of 1-5 μm modified magnetic hybrid filler, 100-120 parts by weight of nylon matrix resin, 2-3 parts by weight of lubricant and 0.3-0.5 parts by weight of antioxidant; The functionalized modified graphene is composed of 10-12 parts by weight of graphite powder and 0.2-0.3 parts by weight of a functionalized modifier; The functionalized modifier is prepared by microwave reaction of 8.2-8.5 parts by weight of N-methylimidazole and 28.8-31.2 parts by weight of 3-chloropropyltriethoxysilane; The modified magnetic hybrid filler is prepared by pre-treating boron nitride with PSS and then dispersing it in deionized water. Then, an iron salt solution and 1,6-hexanediamine are added to react to prepare a magnetic hybrid filler. The magnetic hybrid filler is then treated with plasma fluorination and then modified with sodium ricinoleate to prepare a modified magnetic hybrid filler.

2. A method for preparing the graphene-modified polymer thermally conductive plastic according to claim 1, characterized in that: The steps include: S1: Preparation of functionalized modifiers First, N-methylimidazole and 3-chloropropyltriethoxysilane are subjected to microwave reaction, and after the reaction is completed, the reaction is washed and dried by rotary evaporation to obtain a functionalized modifier; S2: Functionalized modified graphene The functionalized modifier and graphite powder are separated into anhydrous ethanol, and then ball milled to obtain functionalized modified graphene; S3: Preparation and modification of magnetic hybrid fillers The ultrasonically treated boron nitride powder is added to a 10-12 wt% PSS aqueous solution, and the pH is adjusted to 3 to react to prepare a pretreated boron nitride powder. The pretreated boron nitride powder is then dispersed in deionized water, and a 7.5-8 wt% iron salt solution and 1,6-hexanediamine are added to react to obtain a magnetic hybrid filler. The magnetic hybrid filler is then treated with plasma fluorination, and the magnetic hybrid filler is modified and fluorinated with sodium ricinoleate to prepare a modified magnetic hybrid filler. S4: Preparation of polymer thermal conductive plastics Functionalized modified graphene, modified magnetic hybrid filler, nylon matrix resin, lubricant and antioxidant are mixed and then melt-reacted and extruded. After the melt is extruded through a die, a DC magnetic field of 0.3-0.5T perpendicular to the extrusion direction is applied to it, and heat treatment is performed at the same time. After the heat treatment, it is naturally cooled to room temperature to obtain a polymer thermal conductive plastic.

3. The method for preparing a graphene-modified polymer thermally conductive plastic according to claim 2, wherein: Step S1: Preparation of a functionalized modifier, specifically comprising the following steps: S1.1: 8.2-8.5 parts by weight of N-methylimidazole and 28.8-31.2 parts by weight of 3-chloropropyltriethoxysilane were added to a three-necked flask and magnetically stirred at room temperature for 30-40 minutes. The mixture was then placed in a microwave reactor and microwaved at a power of 200-220 W for 20-30 seconds. The microwave treatment was stopped and stirred for 30-40 seconds. The above operation was repeated for microwave treatment for an effective microwave time of 5-6 minutes to obtain a reaction mixture. S1.2: After the reaction mixture is cooled to room temperature, it is washed with ethyl acetate and petroleum ether 2-3 times respectively, then rotary evaporated, and finally vacuum dried at 80-82°C to obtain a functionalized modifier.

4. The method for preparing a graphene-modified polymer thermally conductive plastic according to claim 3, wherein: Step S2 functionalizes and modifies graphene, specifically comprising the following steps: S2.1: Add 10-12 parts by weight of graphite powder and 0.2-0.3 parts by weight of a functional modifier to 50-60 parts by weight of anhydrous ethanol, and ultrasonically disperse for 20-30 minutes to obtain a dispersion; S2.2: Add the dispersion into a ball mill, then add zirconium oxide grinding balls with a ball-to-material mass ratio of 10-12:1, then ball mill at 150-180 r / min for 12-14 h, wash the ball milled product with deionized water 2-3 times, then vacuum dry it at 60-65 ° C for 6-8 h, grind and sieve to obtain 20-50 μm functionalized modified graphene.

5. The method for preparing a graphene-modified polymer thermally conductive plastic according to claim 4, characterized in that: Step S3: Preparation and modification of magnetic hybrid filler, specifically comprising the following steps: S3.1: Add 5-8 parts by weight of the ultrasonically treated boron nitride powder to 10-12 parts by weight of a 10-12 wt% PSS aqueous solution, stir and mix for 1-2 hours, then add 1M hydrochloric acid solution dropwise, adjust the pH to 3, and stir and mix again for 1-2 hours. After standing for 12-14 hours, filter, and wash the filtered precipitate with ethanol and deionized water until neutral, and then vacuum dry to obtain pretreated boron nitride powder; S3.2: 10-12 parts by weight of pretreated boron nitride powder is added to deionized water, stirred and dispersed for 10-20 minutes to prepare a 10-12 wt% mixed suspension, then 80-90 parts by weight of a 7.5-8 wt% iron salt solution is added, stirred and mixed for 20-30 minutes, then 15-20 parts by weight of 1,6-hexanediamine is added, and the mixture is allowed to settle for 24-25 hours, then filtered, and the filtered precipitate is washed 2-3 times with ethanol and deionized water, then dried and ground to obtain a magnetic hybrid filler; S3.3: Placing the magnetic hybrid filler in a reactor for plasma fluorination treatment, setting the voltage to 28-30 kV and the frequency to 9-10 kHz, using nitrogen and CF4 at a ratio of 25-26:1, and fluorinating for 10-15 minutes to obtain the fluorinated magnetic hybrid filler; S3.4: Add 2-3 parts by weight of sodium ricinoleate to 10-12 parts by weight of anhydrous ethanol, then stir at 40-60°C for 20-30 minutes, then add 3-5 parts by weight of fluorinated magnetic hybrid filler, continue stirring and mixing for 2-3 hours, and after the reaction is completed, wash with anhydrous ethanol 2-3 times, filter, dry, grind and sieve to obtain a 1-5μm modified magnetic hybrid filler.

6. The method for preparing a graphene-modified polymer thermally conductive plastic according to claim 5, characterized in that: The iron salt solution in step S3.2 is specifically an iron salt solution containing FeCl3 and FeCl2. 2+ with Fe 3+ The molar ratio is 1:

2.

7. The method for preparing a graphene-modified polymer thermally conductive plastic according to claim 4, wherein: Step S4 is the preparation of a polymer thermal conductive plastic, specifically comprising the following steps: S4.1: Place 8-10 parts by weight of functionalized modified graphene and 3-5 parts by weight of modified magnetic hybrid filler in a high-speed mixer, then add 100-120 parts by weight of nylon matrix resin, 2-3 parts by weight of lubricant, and 0.3-0.5 parts by weight of antioxidant, and start the high-speed mixer to mix to prepare a mixture; S4.2: Adding the mixture into a twin-screw extruder barrel, performing a melt reaction and mixing at 180-300°C, extruding the melt through the twin-screw extruder barrel, applying a DC magnetic field of 0.3-0.5T perpendicular to the extrusion direction to the melt after extrusion through a die, and simultaneously performing a heat treatment. After the heat treatment, the melt is naturally cooled to room temperature to obtain a polymer thermal conductive plastic. The heat treatment is specifically as follows: heating to 70-80°C at 2-3°C / min and keeping warm for 10-20 minutes, then heating to 110-125°C at 3-4°C / min and keeping warm for 30-45 minutes, and cooling to 40-45°C at 0.2-0.4°C / min.

8. The method for preparing a graphene-modified polymer thermally conductive plastic according to claim 7, characterized in that: In step S4.1, the lubricant is one or more of calcium stearate and zinc stearate.

9. The method for preparing a graphene-modified polymer thermally conductive plastic according to claim 7, characterized in that: The antioxidant in step S4.1 is one or more of antioxidant 264, antioxidant 1010, and antioxidant 1076.

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