Coated polylactic acid / graphene composite 3D printing filament and its preparation method and application

Abstract

The present invention discloses a coated polylactic acid / graphene composite 3D printing filament and its preparation method and application. The preparation method comprises: mixing graphene with polylactic acid and subjecting the mixture to co-granulation, melt extrusion, wire drawing, cooling and pulling to obtain polylactic acid / graphene composite 3D printing filament; uniformly mixing polylactic acid, polycaprolactone and graphene organic dispersion to obtain graphene-coated dispersion; and contacting the polylactic acid / graphene composite 3D printing filament with the graphene-coated dispersion to obtain coated polylactic acid / graphene composite 3D printing filament. The coated polylactic acid / graphene composite 3D printing filament provided by the present invention constructs a continuous heat conduction path on the surface of the filament, solving the problem of achieving high thermal conductivity at a low filler content.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal conductive materials, and in particular relates to a coated polylactic acid / graphene composite 3D printing filament and a preparation method and application thereof. Background Art

[0002] The rapid development of the fifth generation of wireless communication technology has led to the trend of high power and miniaturization of electronic devices, but the increase in data transmission and information exchange will lead to heat accumulation inside electronic components, thus affecting their operating stability and service life. Thermal conductive materials are materials that can efficiently conduct heat. They have low thermal resistance, high thermal conductivity and good heat transfer performance. Thermal conductive materials can reduce thermal resistance by improving thermal conductivity, thereby achieving rapid heat conduction.

[0003] The preparation of complex heat dissipation devices with light weight and good thermal conductivity is a research hotspot in the prior art. Graphene is an excellent thermal conductive material. Combining it with 3D printing technology has great application potential in the field of thermal management of electronic devices. The patent with publication number CN116828832A discloses a method for preparing a graphene / carbon nanotube / iron tetroxide composite material for thermal conduction and electromagnetic shielding. It is through two steps of hydrothermal reaction and heat treatment: iron tetroxide particles are generated during the hydrothermal reaction, and graphene oxide is wrapped on the surface of the iron tetroxide particles. Carboxylation of carbon nanotubes is connected to the surface of graphene oxide through group reaction. During the process, reduction reaction of graphene oxide and carboxylation of carbon nanotubes occurs simultaneously to form a core-shell multi-level structure. During the drying process, pressing and molding are performed to obtain a graphene / carbon nanotube / iron tetroxide composite material with a relatively thin thickness. The internal structure is that graphene sheets are stacked to wrap iron tetroxide therein, and carbon nanotubes are cross-connected to form a carbon nanotube network; after high-temperature heat treatment, a complete heat conduction path is formed, showing excellent thermal conductivity. The invented material has excellent thermal conductivity and is widely used. However, the preparation process of the thermal conductive material is complicated and it is difficult to use it in complex heat dissipation devices.The patent with publication number CN116904022A discloses a nylon composite material and its preparation method and application, which includes the following components by weight: 80 parts of nylon 6 resin; 8-30 parts of active group grafted rubber; 0.8-7 parts of α-methylstyrene / acrylonitrile / N-phenylmaleimide terpolymer; 15-50 parts of graphite thermal conductive material; and also includes polytetrafluoroethylene tow, the content of which is 5%-20% of the weight of the active group grafted rubber; the tow is continuously distributed in the resin matrix by tow-forming polytetrafluoroethylene, and the active group grafted rubber and the above terpolymer are coated on the polytetrafluoroethylene tow together to form a continuous phase structure running through the entire material, and the graphite thermal conductive material is enriched at the interface between the continuous phase structure and the PA substrate to form a percolation network to obtain good thermal conductivity; the patent with publication number CN116606527A The patent discloses a high thermal conductivity wear-resistant composite material and its preparation method, which is composed of the following raw materials in parts by weight: 8-12 parts of fat pore raw material, 1-2 parts of film-forming agent, 3-5 parts of carbon fiber, 1-2 parts of organic adhesive, 30-35 parts of high boiling point solvent, 1-5 parts of dispersant, 8-12 parts of calcium carbonate powder, 25-30 parts of zirconium corundum fine powder mixture, 3-5 parts of silicon carbide, 3-5 parts of graphene, 5-8 parts of aluminum oxide fine powder, 3-5 parts of polar solvent, 1-3 parts of 30% concentration initiator aqueous solution, 3-5 parts of 3% sodium bicarbonate aqueous solution, 3-5 parts of stabilizer, 1-3 parts of 0.5 mol / L potassium persulfate aqueous solution, 5-7 parts of curing agent, 0.5-2 parts of cross-linking agent, the thermally conductive fillers cooperate with each other to form a good thermal conductive network to obtain higher thermal conductivity; however, the above two methods have problems such as too many types of raw materials, high amount of thermally conductive material added, and complicated preparation methods. Summary of the invention

[0004] The main purpose of the present invention is to provide a coated polylactic acid / graphene composite 3D printing filament and its preparation method and application to overcome the shortcomings of the prior art.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0006] The embodiment of the present invention provides a method for preparing a coated polylactic acid / graphene composite 3D printing filament, which comprises:

[0007] The graphene and polylactic acid are mixed and subjected to blending granulation, melt extrusion, wire drawing, cooling, and pulling to obtain a polylactic acid / graphene composite 3D printing filament;

[0008] The polylactic acid, polycaprolactone and graphene organic dispersion are uniformly mixed to prepare a graphene coating dispersion;

[0009] And, the polylactic acid / graphene composite 3D printing filament is contacted with the graphene coating dispersion liquid to obtain the coated polylactic acid / graphene composite 3D printing filament.

[0010] The embodiment of the present invention also provides a coated polylactic acid / graphene composite 3D printing filament prepared by the aforementioned preparation method, wherein the coated polylactic acid / graphene composite 3D printing filament comprises a polylactic acid / graphene composite 3D printing filament and a graphene coating layer coated on the surface of the polylactic acid / graphene composite 3D printing filament.

[0011] The embodiment of the present invention also provides the application of the aforementioned coated polylactic acid / graphene composite 3D printing filament in the field of thermal management of electronic devices.

[0012] The embodiment of the present invention also provides a method for preparing a 3D printed heat dissipation workpiece, which comprises:

[0013] The aforementioned coated polylactic acid / graphene composite 3D printing filament is provided and printed with a fused deposition modeling 3D printer to obtain a 3D printed heat dissipation workpiece.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) In the present invention, polylactic acid and polycaprolactone are added to a graphene organic dispersion to obtain a graphene-coated dispersion, and then the polylactic acid / graphene filament is pulled through the dispersion at a constant speed to obtain a coated polylactic acid / graphene composite 3D printing filament, so that the graphene is continuously and overlappingly distributed on the surface of the filament, wherein the role of the polylactic acid is to coat the graphene on the surface of the filament to form a sandwich structure, and the role of the polycaprolactone is to increase the viscosity of the dispersion so that the graphene is coated on the surface of the filament without falling off, thereby solving the problem that the graphene needs a high filler content in the resin matrix to construct a continuous heat conduction path;

[0016] (2) The graphene coated on the surface of the coated polylactic acid / graphene composite 3D printing filament in the present invention and the graphene blended inside construct a synergistic thermal conductive network, and heat is quickly transmitted along the constructed synergistic thermal conductive network, which can significantly reduce phonon scattering and improve the tensile and thermal conductivity of the printed part when the amount of graphene is low;

[0017] (3) The method for preparing the coated polylactic acid / graphene composite 3D printing filament provided by the present invention is simple in process, low in cost and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1a-1b is a SEM image of the 3D printing filament prepared in Example 2 of the present invention;

[0020] Figure 2a-2b is a SEM image of the 3D printing filament prepared in Example 4 of the present invention;

[0021] Figure 3a-Figure 3b This is a SEM image of the 3D printing filament prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0022] In view of the defects of the prior art, the inventors of this case have proposed the technical solution of the present invention after long-term research and extensive practice. The surface-coated polylactic acid / graphene filaments are prepared by solution coating, and a continuous heat conduction path is constructed on the surface of the filament, which solves the problem of achieving high thermal conductivity with low filler content. The composite filament is passed through a fused deposition modeling 3D printer to prepare complex heat dissipation components with excellent thermal conductivity.

[0023] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0024] Specifically, as one aspect of the technical solution of the present invention, a method for preparing a coated polylactic acid / graphene composite 3D printing filament includes:

[0025] The graphene and polylactic acid are mixed and subjected to blending granulation, melt extrusion, wire drawing, cooling, and pulling to obtain a polylactic acid / graphene composite 3D printing filament;

[0026] The polylactic acid, polycaprolactone and graphene organic dispersion are uniformly mixed to prepare a graphene coating dispersion;

[0027] And, the polylactic acid / graphene composite 3D printing filament is contacted with the graphene coating dispersion liquid to obtain the coated polylactic acid / graphene composite 3D printing filament.

[0028] In some preferred embodiments, the preparation method specifically comprises:

[0029] The graphene and polylactic acid are mixed in a mass ratio of 0.02 to 0.1:1 and blended and granulated by a twin-screw extruder to obtain blended granules;

[0030] And, the blended pellets are melt-extruded through a single-screw extruder, and then subjected to wire drawing, cooling, and traction treatment to obtain a polylactic acid / graphene composite 3D printing filament.

[0031] Furthermore, the blended pellets are vacuum dried and added to a single-screw extruder, so that the blended pellets are extruded sequentially through mold zone 1, main engine zone 1, main engine zone 2, main engine zone 3 and main engine zone 4; wherein the temperature zones of the single-screw extruder include: the temperature of mold zone 1 is 185-190°C, the temperature of main engine zone 1 is 180-185°C, the temperature of main engine zone 2 is 185-195°C, the temperature of main engine zone 3 is 190-200°C, and the temperature of main engine zone 4 is 195-205°C.

[0032] Furthermore, the screw rotation extrusion speed of the single-screw extruder is 25-40rpm.

[0033] Furthermore, the cooling treatment is carried out in a three-stage water tank cooling manner, wherein the temperature of the first cooling water tank is 50-55°C, the temperature of the second cooling water tank is 40-45°C, and the temperature of the third cooling water tank is room temperature.

[0034] In some preferred embodiments, the preparation method specifically comprises: mixing polylactic acid, polycaprolactone and graphene organic dispersion and stirring at room temperature for 1-2 hours, and then ultrasonically treating for 0.5-1 hour to obtain a graphene-coated dispersion.

[0035] Furthermore, the mass ratio of graphene, polylactic acid and polycaprolactone in the graphene coating dispersion is 2 to 5:1:1.

[0036] In some preferred embodiments, the graphene organic dispersion comprises graphene and an organic solvent.

[0037] Furthermore, the number of graphene layers is 10 to 15, and the lateral size is 5 to 10 μm.

[0038] Further, the organic solvent includes dichloromethane and / or ethanol, but is not limited thereto.

[0039] Furthermore, the content of graphene in the graphene organic dispersion is 20-50 mg / ml.

[0040] In some preferred embodiments, the preparation method specifically comprises: passing the polylactic acid / graphene composite 3D printing filament through the graphene coating dispersion at a constant pulling speed of 10-15 rpm, thereby obtaining a coated polylactic acid / graphene composite 3D printing filament.

[0041] In some preferred embodiments, the melt index of the polylactic acid is 12-18 g / 10 min.

[0042] In some more specific embodiments, the method for preparing the coated polylactic acid / graphene composite 3D printing filament comprises the following steps:

[0043] (1) Graphene and polylactic acid pellets are mixed at a mass ratio of 0.02:1, blended and granulated by a twin-screw extruder, and dried to obtain blended pellets, which are added to a single-screw extruder for melt extrusion, and then drawn, cooled, and pulled to obtain a polylactic acid / graphene composite 3D printing filament with a diameter of 1.75±0.05 mm.

[0044] (2) Adding polylactic acid and polycaprolactone into the graphene organic dispersion, stirring at room temperature for 1-2 hours, and ultrasonicating for 0.5 hours to prepare a graphene-coated dispersion.

[0045] (3) The polylactic acid / graphene composite 3D printing filament is passed through the graphene coating dispersion at a constant pulling speed to obtain a coated polylactic acid / graphene composite 3D printing filament.

[0046] In the prior art, resin matrix / graphene composite materials are usually prepared by direct melt blending. However, the graphene particle size is small and the interaction between particles is large, which easily leads to agglomeration. Therefore, a high content of filler needs to be added to the resin matrix of graphene to obtain ideal thermal conductivity. The present invention focuses on this technical problem. First, polylactic acid / graphene filaments are prepared, polylactic acid and polycaprolactone are added to a graphene organic dispersion and ultrasonically stirred to prepare a graphene coating dispersion, and then the polylactic acid / graphene filaments are passed through the graphene coating dispersion at a constant pulling speed to obtain a coated polylactic acid / graphene composite 3D printing filament.

[0047] Preferably, in step (1), the vacuum-dried graphene / polylactic acid composite pellets are added to a single-screw extruder, and the raw materials are extruded sequentially through mold zone 1, main engine zone 1, main engine zone 2, main engine zone 3 and main engine zone 4, and the temperature of the single-screw extruder is set as follows: the temperature of mold zone 1 is 185-190°C, the temperature of main engine zone 1 is 180-185°C, the temperature of main engine zone 2 is 185-195°C, the temperature of main engine zone 3 is 190-200°C, and the temperature of main engine zone 4 is 195-205°C.

[0048] Specifically, the screw rotation extrusion speed of the single-screw extruder is 25-40rpm; the parameters of the cooling stage are set as: controlling the cooling temperature of the first section to 50-60°C, controlling the cooling temperature of the second section to 40-45°C, and controlling the cooling temperature of the third section to 25-30°C; further preferably, controlling the cooling temperature of the first section to 55°C, controlling the cooling temperature of the second section to 45°C, and controlling the cooling temperature of the third section to 25°C.

[0049] Specifically, the melt index of the polylactic acid pellets is 12-18 g / 10 min. The mass ratio of the graphene to the polylactic acid pellets is 0.02:1.

[0050] Preferably, in step (2), polylactic acid and polycaprolactone are added to the graphene organic dispersion, stirred at room temperature for 1-2 hours, and ultrasonicated for 0.5-1 hour to prepare the graphene-coated dispersion, thereby ensuring the dispersion performance of graphene in the organic solvent and the thermal conductivity of the prepared wire.

[0051] Specifically, the mass ratio of graphene to polylactic acid and polycaprolactone in the graphene organic dispersion is 2 to 5:1:1. Preferably, the organic solvent includes dichloromethane and ethanol. The graphene in the graphene-coated dispersion prepared within the above mass ratio range has excellent dispersibility.

[0052] Preferably, in step (3), the polylactic acid / graphene composite 3D printing filament is passed through the graphene coating dispersion at a constant pulling speed to obtain the coated polylactic acid / graphene composite 3D printing filament.

[0053] Specifically, the pulling speed is 10-15 rpm. Further preferably, the pulling speed is controlled to be 12 rpm. The coated polylactic acid / graphene composite 3D printing filament prepared at the above pulling speed has a uniform filament diameter and excellent thermal conductivity.

[0054] Another aspect of an embodiment of the present invention further provides a coated polylactic acid / graphene composite 3D printing filament prepared by the aforementioned preparation method, wherein the coated polylactic acid / graphene composite 3D printing filament comprises a polylactic acid / graphene composite 3D printing filament and a graphene coating layer coated on the surface of the polylactic acid / graphene composite 3D printing filament.

[0055] Furthermore, the diameter of the polylactic acid / graphene composite 3D printing filament is 1.75±0.05 mm.

[0056] Furthermore, the thickness of the graphene coating layer is 10 to 50 μm.

[0057] Furthermore, the thermal conductivity of the coated polylactic acid / graphene composite 3D printing filament is 0.96 to 1.52 W / (m·K).

[0058] Furthermore, the mass ratio of graphene in the polylactic acid / graphene composite 3D printing filament to graphene in the graphene coating layer is 2-10:50-71.

[0059] Another aspect of the embodiments of the present invention further provides the application of the aforementioned coated polylactic acid / graphene composite 3D printing filament in the field of thermal management of electronic devices.

[0060] Another aspect of the embodiments of the present invention further provides a method for preparing a 3D printed heat dissipation workpiece, which comprises:

[0061] The aforementioned coated polylactic acid / graphene composite 3D printing filament is provided and printed with a fused deposition modeling 3D printer to obtain a 3D printed heat dissipation workpiece.

[0062] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and drawings. This embodiment is implemented on the premise of the technical solution of the invention, and a detailed implementation method and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0063] Unless otherwise specified, the experimental materials used in the following examples can be purchased from conventional biochemical reagent companies.

[0064] In the examples and comparative examples, the melt index of the polylactic acid pellets used was 12-18 g / 10 min.

[0065] Example 1

[0066] (1) adding vacuum-dried graphene / polylactic acid composite pellets (the mass ratio of graphene to polylactic acid pellets is 0.02:1) into a single screw extruder, and extruding the raw materials through the mold zone 1, the main engine zone 1, the main engine zone 2, the main engine zone 3 and the main engine zone 4 in sequence, the temperature of the single screw extruder is set as follows: the temperature of the mold zone 1 is 185°C, the temperature of the main engine zone 1 is 180°C, the temperature of the main engine zone 2 is 185°C, the temperature of the main engine zone 3 is 190°C, the temperature of the main engine zone 4 is 195°C, the screw rotation extrusion speed is 35rpm, the first stage cooling temperature is controlled at 55°C, the second stage cooling temperature is controlled at 45°C, and the third stage cooling temperature is controlled at 25°C. After extrusion, wire drawing, cooling, and pulling, a polylactic acid / graphene composite 3D printing filament with a diameter of 1.75±0.05mm is obtained;

[0067] (2) adding polylactic acid and polycaprolactone to a graphene dichloromethane dispersion (the mass ratio of graphene to polylactic acid and polycaprolactone is 2:1:1), stirring at room temperature for 1 hour, and ultrasonicating for 0.5 hour to obtain a graphene-coated dispersion;

[0068] (3) The polylactic acid / graphene composite 3D printing filament is passed through the graphene coating dispersion at 12 rpm to obtain a coated polylactic acid / graphene composite 3D printing filament.

[0069] Example 2

[0070] (1) adding vacuum-dried graphene / polylactic acid composite pellets (the mass ratio of graphene to polylactic acid pellets is 0.02:1) into a single screw extruder, and extruding the raw materials through the mold zone 1, the main engine zone 1, the main engine zone 2, the main engine zone 3 and the main engine zone 4 in sequence, the temperature of the single screw extruder is set as follows: the temperature of the mold zone 1 is 185°C, the temperature of the main engine zone 1 is 180°C, the temperature of the main engine zone 2 is 185°C, the temperature of the main engine zone 3 is 190°C, the temperature of the main engine zone 4 is 195°C, the screw rotation extrusion speed is 35rpm, the first stage cooling temperature is controlled at 55°C, the second stage cooling temperature is controlled at 45°C, and the third stage cooling temperature is controlled at 25°C. After extrusion, wire drawing, cooling, and pulling, a polylactic acid / graphene composite 3D printing filament with a diameter of 1.75±0.05mm is obtained;

[0071] (2) adding polylactic acid and polycaprolactone to a graphene dichloromethane dispersion (the mass ratio of graphene to polylactic acid and polycaprolactone is 3:1:1), stirring at room temperature for 1 hour, and ultrasonicating for 0.5 hour to obtain a graphene-coated dispersion;

[0072] (3) The polylactic acid / graphene composite 3D printing filament was passed through the graphene coating dispersion at 12 rpm to obtain a coated polylactic acid / graphene composite 3D printing filament (SEM image as shown in FIG. Figure 1a-1b shown).

[0073] Example 3

[0074] (1) adding vacuum-dried graphene / polylactic acid composite pellets (the mass ratio of graphene to polylactic acid pellets is 0.02:1) into a single screw extruder, and extruding the raw materials through the mold zone 1, the main engine zone 1, the main engine zone 2, the main engine zone 3 and the main engine zone 4 in sequence, the temperature of the single screw extruder is set as follows: the temperature of the mold zone 1 is 188°C, the temperature of the main engine zone 1 is 183°C, the temperature of the main engine zone 2 is 190°C, the temperature of the main engine zone 3 is 195°C, the temperature of the main engine zone 4 is 200°C, the screw rotation extrusion speed is 35rpm, the first stage cooling temperature is controlled at 55°C, the second stage cooling temperature is controlled at 45°C, and the third stage cooling temperature is controlled at 25°C. After extrusion, wire drawing, cooling, and pulling, a polylactic acid / graphene composite 3D printing filament with a diameter of 1.75±0.05mm is obtained;

[0075] (2) adding polylactic acid and polycaprolactone to a graphene ethanol dispersion (the mass ratio of graphene to polylactic acid and polycaprolactone is 4:1:1), stirring at room temperature for 1 hour, and ultrasonicating for 0.5 hour to obtain a graphene-coated dispersion;

[0076] (3) The polylactic acid / graphene composite 3D printing filament is passed through the graphene coating dispersion at 12 rpm to obtain a coated polylactic acid / graphene composite 3D printing filament.

[0077] Example 4

[0078] (1) adding vacuum-dried graphene / polylactic acid composite pellets (the mass ratio of graphene to polylactic acid pellets is 0.02:1) into a single screw extruder, and extruding the raw materials through the mold zone 1, the main engine zone 1, the main engine zone 2, the main engine zone 3 and the main engine zone 4 in sequence, the temperature of the single screw extruder is set as follows: the temperature of the mold zone 1 is 188°C, the temperature of the main engine zone 1 is 183°C, the temperature of the main engine zone 2 is 190°C, the temperature of the main engine zone 3 is 195°C, the temperature of the main engine zone 4 is 200°C, the screw rotation extrusion speed is 35rpm, the first stage cooling temperature is controlled at 55°C, the second stage cooling temperature is controlled at 45°C, and the third stage cooling temperature is controlled at 25°C. After extrusion, wire drawing, cooling, and pulling, a polylactic acid / graphene composite 3D printing filament with a diameter of 1.75±0.05mm is obtained;

[0079] (2) adding polylactic acid and polycaprolactone to a graphene ethanol dispersion (the mass ratio of graphene to polylactic acid and polycaprolactone is 5:1:1), stirring at room temperature for 1 hour, and ultrasonicating for 0.5 hour to obtain a graphene-coated dispersion;

[0080] (3) The polylactic acid / graphene composite 3D printing filament was passed through the graphene coating dispersion at 12 rpm to obtain a coated polylactic acid / graphene composite 3D printing filament (SEM image as shown in FIG. Figure 2a-2b shown).

[0081] Example 5

[0082] (1) adding vacuum-dried graphene / polylactic acid composite pellets (the mass ratio of graphene to polylactic acid pellets is 0.02:1) into a single screw extruder, and extruding the raw materials through the mold zone 1, the main engine zone 1, the main engine zone 2, the main engine zone 3 and the main engine zone 4 in sequence, the temperature of the single screw extruder is set as follows: the temperature of the mold zone 1 is 190°C, the temperature of the main engine zone 1 is 185°C, the temperature of the main engine zone 2 is 195°C, the temperature of the main engine zone 3 is 200°C, the temperature of the main engine zone 4 is 205°C, the screw rotation extrusion speed is 35rpm, the first stage cooling temperature is controlled at 55°C, the second stage cooling temperature is controlled at 45°C, and the third stage cooling temperature is controlled at 25°C. After extrusion, wire drawing, cooling, and pulling, a polylactic acid / graphene composite 3D printing filament with a diameter of 1.75±0.05mm is obtained;

[0083] (2) adding polylactic acid and polycaprolactone to a graphene dichloromethane dispersion (the mass ratio of graphene to polylactic acid and polycaprolactone is 3:1:1), stirring at room temperature for 1 hour, and ultrasonicating for 0.5 hour to obtain a graphene-coated dispersion;

[0084] (3) The polylactic acid / graphene composite 3D printing filament is passed through the graphene coating dispersion at 10 rpm to obtain a coated polylactic acid / graphene composite 3D printing filament.

[0085] Example 6

[0086] (1) adding vacuum-dried graphene / polylactic acid composite pellets (the mass ratio of graphene to polylactic acid pellets is 0.02:1) into a single screw extruder, and extruding the raw materials through the mold zone 1, the main engine zone 1, the main engine zone 2, the main engine zone 3 and the main engine zone 4 in sequence, the temperature of the single screw extruder is set as follows: the temperature of the mold zone 1 is 190°C, the temperature of the main engine zone 1 is 185°C, the temperature of the main engine zone 2 is 195°C, the temperature of the main engine zone 3 is 200°C, the temperature of the main engine zone 4 is 205°C, the screw rotation extrusion speed is 35rpm, the first stage cooling temperature is controlled at 55°C, the second stage cooling temperature is controlled at 45°C, and the third stage cooling temperature is controlled at 25°C. After extrusion, wire drawing, cooling, and pulling, a polylactic acid / graphene composite 3D printing filament with a diameter of 1.75±0.05mm is obtained;

[0087] (2) adding polylactic acid and polycaprolactone to a graphene dichloromethane dispersion (the mass ratio of graphene to polylactic acid and polycaprolactone is 3:1:1), stirring at room temperature for 1 hour, and ultrasonicating for 0.5 hour to obtain a graphene-coated dispersion;

[0088] (3) The polylactic acid / graphene composite 3D printing filament is passed through the graphene coating dispersion at 15 rpm to obtain a coated polylactic acid / graphene composite 3D printing filament.

[0089] Comparative Example 1

[0090] (1) Adding vacuum-dried polylactic acid pellets to a single-screw extruder, the raw materials are sequentially extruded through the mold zone 1, the main engine zone 1, the main engine zone 2, the main engine zone 3 and the main engine zone 4. The temperature of the single-screw extruder is set as follows: the temperature of the mold zone 1 is 185°C, the temperature of the main engine zone 1 is 180°C, the temperature of the main engine zone 2 is 185°C, the temperature of the main engine zone 3 is 190°C, the temperature of the main engine zone 4 is 195°C, the screw rotation extrusion speed is 35rpm, the first stage cooling temperature is controlled at 55°C, the second stage cooling temperature is controlled at 45°C, and the third stage cooling temperature is controlled at 25°C. After extrusion, wire drawing, cooling and pulling, a polylactic acid filament with a diameter of 1.75±0.05 mm is obtained (SEM picture as shown in FIG. Figure 3a-Figure 3b shown).

[0091] Comparative Example 2

[0092] (1) Adding vacuum-dried graphene / polylactic acid composite pellets (the mass ratio of graphene to polylactic acid pellets is 0.06:1) into a single screw extruder, and the raw materials are extruded through the mold zone 1, the main engine zone 1, the main engine zone 2, the main engine zone 3 and the main engine zone 4 in sequence. The temperature of the single screw extruder is set as follows: the temperature of the mold zone 1 is 185°C, the temperature of the main engine zone 1 is 180°C, the temperature of the main engine zone 2 is 185°C, the temperature of the main engine zone 3 is 190°C, and the temperature of the main engine zone 4 is 195°C. The screw rotation extrusion speed is 35 rpm, the first stage cooling temperature is controlled at 55°C, the second stage cooling temperature is controlled at 45°C, and the third stage cooling temperature is controlled at 25°C. After extrusion, wire drawing, cooling, and traction, a polylactic acid / graphene filament with a diameter of 1.75±0.05 mm is obtained.

[0093] Comparative Example 3: Pure polylactic acid inside

[0094] (1) Adding vacuum-dried polylactic acid pellets to a single-screw extruder, extruding the raw materials through the mold zone 1, the main engine zone 1, the main engine zone 2, the main engine zone 3 and the main engine zone 4 in sequence, the temperature of the single-screw extruder is set to: the temperature of the mold zone 1 is 185°C, the temperature of the main engine zone 1 is 180°C, the temperature of the main engine zone 2 is 185°C, the temperature of the main engine zone 3 is 190°C, the temperature of the main engine zone 4 is 195°C, the screw rotation extrusion speed is 35rpm, the first stage cooling temperature is controlled at 55°C, the second stage cooling temperature is controlled at 45°C, and the third stage cooling temperature is controlled at 25°C. After extrusion, wire drawing, cooling, and pulling, a polylactic acid 3D printing filament with a diameter of 1.75±0.05mm is obtained;

[0095] (2) adding polylactic acid and polycaprolactone to a graphene dichloromethane dispersion (the mass ratio of graphene to polylactic acid and polycaprolactone is 2:1:1), stirring at room temperature for 1 hour, and ultrasonicating for 0.5 hour to obtain a graphene-coated dispersion;

[0096] (3) The polylactic acid 3D printing filament is passed through the graphene coating dispersion at 12 rpm to obtain a coated polylactic acid / graphene composite 3D printing filament.

[0097] Comparative Example 4: The coating layer does not contain polycaprolactone

[0098] (1) adding vacuum-dried graphene / polylactic acid composite pellets (the mass ratio of graphene to polylactic acid pellets is 0.02:1) into a single screw extruder, and extruding the raw materials through the mold zone 1, the main engine zone 1, the main engine zone 2, the main engine zone 3 and the main engine zone 4 in sequence, the temperature of the single screw extruder is set as follows: the temperature of the mold zone 1 is 185°C, the temperature of the main engine zone 1 is 180°C, the temperature of the main engine zone 2 is 185°C, the temperature of the main engine zone 3 is 190°C, the temperature of the main engine zone 4 is 195°C, the screw rotation extrusion speed is 35rpm, the first stage cooling temperature is controlled at 55°C, the second stage cooling temperature is controlled at 45°C, and the third stage cooling temperature is controlled at 25°C. After extrusion, wire drawing, cooling, and pulling, a polylactic acid / graphene composite 3D printing filament with a diameter of 1.75±0.05mm is obtained;

[0099] (2) adding polylactic acid to a graphene dichloromethane dispersion (the mass ratio of graphene to polylactic acid is 2:2), stirring at room temperature for 1 hour, and ultrasonicating for 0.5 hour to obtain a graphene-coated dispersion;

[0100] (3) The polylactic acid / graphene composite 3D printing filament is passed through the graphene coating dispersion at 12 rpm to obtain a coated polylactic acid / graphene composite 3D printing filament.

[0101] Comparative Example 5: The coating layer does not contain graphene

[0102] (1) adding vacuum-dried graphene / polylactic acid composite pellets (the mass ratio of graphene to polylactic acid pellets is 0.02:1) into a single screw extruder, and extruding the raw materials through the mold zone 1, the main engine zone 1, the main engine zone 2, the main engine zone 3 and the main engine zone 4 in sequence, the temperature of the single screw extruder is set as follows: the temperature of the mold zone 1 is 185°C, the temperature of the main engine zone 1 is 180°C, the temperature of the main engine zone 2 is 185°C, the temperature of the main engine zone 3 is 190°C, the temperature of the main engine zone 4 is 195°C, the screw rotation extrusion speed is 35rpm, the first stage cooling temperature is controlled at 55°C, the second stage cooling temperature is controlled at 45°C, and the third stage cooling temperature is controlled at 25°C. After extrusion, wire drawing, cooling, and pulling, a polylactic acid / graphene composite 3D printing filament with a diameter of 1.75±0.05mm is obtained;

[0103] (2) adding polylactic acid and polycaprolactone into dichloromethane (the mass ratio of polylactic acid to polycaprolactone is 1:1), stirring at room temperature for 1 hour, and ultrasonicating for 0.5 hour to obtain a dispersion;

[0104] (3) The polylactic acid / graphene composite 3D printing filament is passed through the dispersion liquid at 12 rpm to obtain a coated polylactic acid / graphene composite 3D printing filament.

[0105] Sample analysis

[0106] The filaments prepared in the embodiment and the comparative example were used to print thermal conductivity test specimens using a fused deposition modeling 3D printer, with the printing temperature set at 200° C., the platform temperature at 50° C., the printing speed at 5 mm / s, and the filling rate at 100%.

[0107] The sample size for testing thermal conductivity is 10mm*10mm*1.5mm, the printing direction is 0 degrees, and the tensile performance test adopts ISO527 / 2 / 1A test standard, the printing direction is 0 degrees. The results are shown in Table 1:

[0108] Table 1 Thermal conductivity and tensile properties of wires in Examples 1-6 and Comparative Examples 1-5

[0109] serial number Thermal conductivity (W / (mK)) Tensile properties (MPa) Example 1 0.96 46 Example 2 1.15 48 Example 3 1.30 51 Example 4 1.52 47 Example 5 1.27 45 Example 6 1.06 49 Comparative Example 1 0.30 40 Comparative Example 2 0.45 32 Comparative Example 3 0.63 35 Comparative Example 4 0.55 38 Comparative Example 5 0.32 42

[0110] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0111] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical deformation made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a coated polylactic acid / graphene composite 3D printing filament, characterized in that: include: The graphene and polylactic acid are mixed and subjected to blending granulation, melt extrusion, wire drawing, cooling, and pulling to obtain a polylactic acid / graphene composite 3D printing filament; The polylactic acid, polycaprolactone and graphene organic dispersion are uniformly mixed to obtain a graphene coating dispersion; And, the polylactic acid / graphene composite 3D printing filament is contacted with the graphene coating dispersion liquid to obtain the coated polylactic acid / graphene composite 3D printing filament.

2. The preparation method according to claim 1, characterized in that: Specifically include: The graphene and polylactic acid are mixed in a mass ratio of 0.02 to 0.1:1 and blended and granulated by a twin-screw extruder to obtain blended granules; And, the blended pellets are melt-extruded through a single-screw extruder, and then subjected to wire drawing, cooling, and traction treatment to obtain a polylactic acid / graphene composite 3D printing filament.

3. The preparation method according to claim 2, characterized in that: The blended pellets are vacuum dried and added into a single screw extruder, and the blended pellets are extruded sequentially through a mold zone 1, a main engine zone 1, a main engine zone 2, a main engine zone 3 and a main engine zone 4; wherein the temperature zones of the single screw extruder include: a temperature of the mold zone 1 of 185 to 190° C., a temperature of the main engine zone 1 of 180 to 185° C., a temperature of the main engine zone 2 of 185 to 195° C., a temperature of the main engine zone 3 of 190 to 200° C., and a temperature of the main engine zone 4 of 195 to 205° C.; And / or, the screw rotation extrusion speed of the single screw extruder is 25-40rpm; And / or, the cooling treatment is carried out by a three-stage water tank cooling method, wherein the temperature of the first cooling water tank is 50-55°C, the temperature of the second cooling water tank is 40-45°C, and the temperature of the third cooling water tank is room temperature.

4. The preparation method according to claim 1, characterized in that: Specifically include: The polylactic acid, polycaprolactone and graphene organic dispersion were mixed and stirred at room temperature for 1-2 hours, and then subjected to ultrasonic treatment for 0.5-1 hour to obtain a graphene-coated dispersion.

5. The preparation method according to claim 4, characterized in that: The mass ratio of graphene, polylactic acid and polycaprolactone in the graphene coating dispersion is 2 to 5:1:1; And / or, the graphene organic dispersion comprises graphene and an organic solvent; wherein the graphene has 10 to 15 layers and a lateral size of 5 to 10 μm; and the organic solvent comprises dichloromethane and / or ethanol; And / or, the content of graphene in the graphene organic dispersion is 20-50 mg / ml.

6. The preparation method according to claim 1, characterized in that: Specifically include: The polylactic acid / graphene composite 3D printing filament is passed through the graphene coating dispersion at a constant pulling speed of 10-15 rpm to obtain a coated polylactic acid / graphene composite 3D printing filament.

7. The preparation method according to claim 1, characterized in that: The melt index of the polylactic acid is 12-18 g / 10 min.

8. The coated polylactic acid / graphene composite 3D printing filament prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The coated polylactic acid / graphene composite 3D printing filament comprises a polylactic acid / graphene composite 3D printing filament and a graphene coating layer coated on the surface of the polylactic acid / graphene composite 3D printing filament.

9. The coated polylactic acid / graphene composite 3D printing filament according to claim 8, characterized in that: The diameter of the polylactic acid / graphene composite 3D printing filament is 1.75±0.05 mm.

10. The coated polylactic acid / graphene composite 3D printing filament according to claim 8, characterized in that: The thickness of the graphene coating layer is 10-50 μm.

11. The coated polylactic acid / graphene composite 3D printing filament according to claim 8, characterized in that: The thermal conductivity of the coated polylactic acid / graphene composite 3D printing filament is 0.96~1.52W / (m·K).

12. The coated polylactic acid / graphene composite 3D printing filament according to claim 8, characterized in that: The mass ratio of graphene in the polylactic acid / graphene composite 3D printing filament to graphene in the graphene coating layer is 2-10:50-71.

13. Application of the coated polylactic acid / graphene composite 3D printing filament according to any one of claims 8 to 12 in the field of thermal management of electronic devices.

14. A method for preparing a 3D printed heat dissipation workpiece, characterized in that: include: Provide a coated polylactic acid / graphene composite 3D printing filament according to any one of claims 8 to 12, and print it with a fused deposition modeling 3D printer to produce a 3D printed heat dissipation workpiece.

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