A 3D printed reduced graphene oxide / polylactic acid composite microwave absorbing wire material and its preparation method

Abstract

The present invention discloses a 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing filament material and a preparation method thereof, belonging to the technical field of wave-absorbing materials. The preparation method includes: (1) preparing a reduced graphene oxide organic dispersion; (2) adding polylactic acid powder into the reduced graphene oxide organic dispersion, heating to 140-180 °C, stirring and keeping warm, then cooling to room temperature, filtering and drying in vacuum to obtain a core-shell type reduced graphene oxide / polylactic acid composite powder; (3) extruding, drawing, cooling and pulling the core-shell type reduced graphene oxide / polylactic acid composite powder to obtain a 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing filament material. By preparing the core-shell type reduced graphene oxide / polylactic acid composite powder, the present invention solves the problems of easy agglomeration of graphene and poor compatibility with resin. Using this composite powder as the raw material, a composite wave-absorbing filament material with excellent mechanical properties and good wave-absorbing properties can be prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave absorbing materials, and particularly relates to a 3D printing reduced graphene oxide / polylactic acid composite microwave absorbing filament and a preparation method thereof. Background Art

[0002] The rapid development of electronic technology has brought great convenience to human life. However, electromagnetic wave radiation has certain impacts on the environment and human health. Microwave absorbing materials refer to a class of functional materials that can absorb and attenuate incident electromagnetic waves, and convert electromagnetic energy into heat energy or other forms of energy for consumption, or cause electromagnetic waves to disappear due to interference.

[0003] Microwave absorbing materials with good microwave absorbing performance, light weight, and wide absorption bandwidth are the research hotspots of the existing technology. Graphene is an excellent microwave absorbing material, and its microwave absorbing performance mainly comes from its unique electromagnetic properties. Moreover, graphene also has broadband microwave absorbing performance and can absorb electromagnetic waves within a relatively wide frequency range.

[0004] Chinese patent document with publication number CN112266593A discloses a degradable bioresin-based microwave absorbing material and a preparation method thereof. The microwave absorbing material comprises the following raw materials in parts by weight: 40-45 parts of a resin matrix, 5-10 parts of a ceramic matrix, 3-5 parts of citric acid, 3-5 parts of iron tetroxide, 10-15 parts of nano-graphene, 4-6 parts of a coupling agent, and 2-4 parts of a dispersant. The invention selects polylactic acid or polybutylene succinate as the resin matrix, and adds a ceramic matrix, iron tetroxide, and nano-graphene as absorbents through reasonable proportioning to expand the absorption band range of electromagnetic waves and enhance the absorption rate. The material of the invention is simple to prepare, can be mass-produced, and has wide applications. However, the microwave absorbing material is prepared by a conventional mixing method, and there may be a problem of uneven dispersion of absorbents.

[0005] The Chinese patent document with the publication number CN106751836A discloses a graphene composite wave-absorbing polysulfide sealant, which consists of two components: a base paste and a vulcanizing paste. The base paste contains liquid polysulfide rubber, graphene, carbonyl iron powder, and epoxy resin; the vulcanizing paste contains manganese dioxide, dibutyl phthalate, accelerator DPG, and stearic acid. The composite wave-absorbing polysulfide sealant prepared by ultrasonic treatment and dispersion of graphene in the base paste has good radar wave absorption performance at 1 GHz - 18 GHz; the Chinese patent document with the publication number CN114071982A discloses a preparation method of a honeycomb-like reduced graphene oxide foam / nickel nanoparticle wave-absorbing agent. The wave-absorbing agent uses honeycomb-like reduced graphene oxide foam as a carrier, and nickel nanoparticles with an average particle size of 80 nm are anchored and loaded on the reduced graphene oxide foam; the composite wave-absorbing agent has the characteristics of high specific surface area and low density, and the electromagnetic microwave absorption effect can be adjusted; however, the above two methods have problems such as too many types of raw materials and complicated preparation methods. Summary of the Invention

[0006] The present invention provides a preparation method of a 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing filament. By preparing core-shell type reduced graphene oxide / polylactic acid composite powder, the problems of easy agglomeration of graphene and poor compatibility with resin are solved. Using the core-shell type reduced graphene oxide / polylactic acid composite powder as raw material, a composite wave-absorbing filament with excellent mechanical properties and good wave-absorbing performance can be prepared.

[0007] The specific technical solutions adopted are as follows:

[0008] A preparation method of a 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing filament, comprising the following steps:

[0009] (1) Adding graphene oxide to water to obtain a graphene oxide aqueous dispersion, subjecting the graphene oxide aqueous dispersion to freeze-drying to obtain graphene oxide powder, and further reducing it to obtain reduced graphene oxide powder; adding the reduced graphene oxide powder to an organic solvent, stirring and ultrasonicating to obtain a reduced graphene oxide organic dispersion with a mass concentration of 20 - 65 wt%.

[0010] (2) Adding polylactic acid powder to the reduced graphene oxide organic dispersion, heating to 140 - 180 °C, stirring and keeping warm for 1 - 3 hours, then cooling to room temperature, filtering and drying in vacuum to obtain core-shell type reduced graphene oxide / polylactic acid composite powder.

[0011] (3) The vacuum-dried core-shell type reduced graphene oxide / polylactic acid composite powder is extruded, drawn, cooled, and tractioned to obtain a 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing filament with a diameter of 1.75 ± 0.05 mm.

[0012] In the prior art, the method of mixing graphene with a resin matrix is usually direct melt blending. However, graphene has a small particle size, large interaction between particles, and is prone to agglomeration. Moreover, there is a large density difference between graphene and the resin matrix, and their compatibility is also poor. Therefore, it is difficult to uniformly disperse graphene in the resin matrix, resulting in poor mechanical properties and wave absorption properties of the composite material. In view of this technical problem, the present invention first prepares a well-dispersed reduced graphene oxide organic dispersion liquid, adds polylactic acid powder to the reduced graphene oxide organic dispersion liquid, then raises the temperature to the semi-molten state of polylactic acid, so that the reduced graphene oxide adheres to the surface of the polylactic acid powder, and then controllably cools and dries to obtain a core-shell type reduced graphene oxide / polylactic acid composite powder; furthermore, a composite wave-absorbing filament with excellent mechanical properties and good wave absorption properties is prepared.

[0013] In step (1), freeze-drying can maintain the dispersion of graphene oxide sheets, avoid the agglomeration of graphene oxide sheets, and thus ensure the dispersion performance of reduced graphene oxide in organic solvents and the wave absorption performance of the prepared composite wave-absorbing filaments.

[0014] Preferably, the organic solvents include methanol, ethanol, acetonitrile, formic acid, acetic acid, formamide, acetamide, etc.

[0015] Specifically, the melt index of the polylactic acid powder is 10-16 g / 10 min.

[0016] The mass ratio of reduced graphene oxide to polylactic acid powder in the reduced graphene oxide organic dispersion liquid is 0.01-0.14:1. The composite wave-absorbing filaments prepared within the above mass ratio range have both excellent wave absorption properties and mechanical properties.

[0017] Preferably, in step (2), the cooling parameter is: the cooling rate is 1-10 °C / min.

[0018] After raising the temperature to the semi-molten state of polylactic acid, the surface of the polylactic acid powder softens and becomes sticky. By stirring, the reduced graphene oxide adheres to the polylactic acid powder. When the temperature decreases, the polylactic acid powder re-solidifies. At this time, the reduced graphene oxide is fused on the polylactic acid powder, and a core-shell structure composite powder with polylactic acid powder as the core and reduced graphene oxide as the shell is obtained.

[0019] In step (3), the vacuum-dried core-shell type reduced graphene oxide / polylactic acid composite powder of the raw materials is added to a single-screw extruder, and the raw materials are successively extruded through the first zone of the die, the first zone of the main machine, the second zone of the main machine, the third zone of the main machine, and the fourth zone of the main machine. The parameter settings of the single-screw extruder are as follows: the temperature of the first zone of the die is 190-220 °C, the temperature of the first zone of the main machine is 185-215 °C, the temperature of the second zone of the main machine is 190-225 °C, the temperature of the third zone of the main machine is 200-230 °C, and the temperature of the fourth zone of the main machine is 200-230 °C.

[0020] Specifically, the screw rotation and extrusion speed of the single-screw extruder is 6-10 rpm; the parameter settings in the cooling stage are as follows: the temperature of the first-stage cooling is controlled at 40-60 °C, and the temperature of the second-stage cooling is controlled at 20-50 °C; more preferably, the temperature of the first-stage cooling is controlled at 50 °C, and the temperature of the second-stage cooling is controlled at 40 °C.

[0021] The present invention also provides a 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing wire prepared by the preparation method of the 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing wire described above.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) In the present invention, polylactic acid powder is added to a well-dispersed reduced graphene oxide organic dispersion liquid, then the temperature is raised to the semi-molten state of polylactic acid, and then the temperature is controllably decreased and dried to obtain a core-shell type reduced graphene oxide / polylactic acid composite powder, which solves the problem that it is difficult to disperse graphene and resin matrix evenly by direct melt blending.

[0024] (2) Reduced graphene oxide is uniformly dispersed with the composite powder. After extrusion, wire drawing, cooling, and traction, a uniformly dispersed reduced graphene oxide network structure is formed in the wire, thereby improving the interconnectivity between reduced graphene oxides, and improving the mechanical and wave-absorbing properties of the printed parts with a lower amount of reduced graphene oxide used.

[0025] (3) The method of the present invention has a simple process, low cost, is easy to implement, and is convenient for large-scale production. Description of the Drawings

[0026] Figure 1 It is a SEM image of the 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing wire in Example 2.

[0027] Figure 2 It is a SEM image of the 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing wire in Example 4.

[0028] Figure 3SEM image of the 3D printed reduced graphene oxide / polylactic acid composite microwave absorbing filaments in Example 6. Detailed implementation manners

[0029] The present invention will be further clarified below in conjunction with examples and accompanying drawings. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. The operation methods without specific conditions noted in the following examples are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0030] In the examples and comparative examples, the melt index of the polylactic acid powder used is 10 - 16 g / 10 min.

[0031] Example 1

[0032] (1) Graphene oxide was added to water to obtain a graphene oxide aqueous dispersion. The graphene oxide aqueous dispersion was freeze-dried to obtain graphene oxide powder, which was further reduced to obtain reduced graphene oxide powder (the reduction method can adopt hydrothermal reduction method, high-temperature reduction method, etc.); the reduced graphene oxide powder was added to an ethanol solvent, and stirred and ultrasonicated for 3 hours to obtain a reduced graphene oxide organic dispersion with a mass concentration of 20 wt%;

[0033] (2) Polylactic acid powder was added to the above-mentioned reduced graphene oxide organic dispersion (the mass ratio of reduced graphene oxide to polylactic acid powder in the reduced graphene oxide organic dispersion was 12:88). The temperature was raised to 140 °C, stirred and kept warm for 1 hour, then cooled to room temperature at a rate of 5 °C / min. After filtration, it was vacuum-dried to obtain core-shell reduced graphene oxide / polylactic acid composite powder;

[0034] (3) The vacuum-dried reduced graphene oxide / polylactic acid composite powder was added to a single-screw extruder, and it was extruded successively through the first die zone, the first main zone, the second main zone, the third main zone and the fourth main zone of the extruder. The temperature of the first die zone of the single-screw extruder was set at 205 °C, the temperature of the first main zone was 200 °C, the temperature of the second main zone was 205 °C, the temperature of the third main zone was 210 °C, the temperature of the fourth main zone was 210 °C, the screw rotation and extrusion speed was 6 rpm, the temperature of the first-stage cooling was controlled at 55 °C, and the temperature of the second-stage cooling was controlled at 40 °C. After extrusion, wire drawing, cooling and traction, 3D printed reduced graphene oxide / polylactic acid composite microwave absorbing filaments with a diameter of 1.75 ± 0.05 mm were obtained.

[0035] Example 2

[0036] (1) Graphene oxide is added to water to obtain a graphene oxide aqueous dispersion. The graphene oxide aqueous dispersion is freeze-dried to obtain graphene oxide powder, which is further reduced to obtain reduced graphene oxide powder. The reduced graphene oxide powder is added to an ethanol solvent, stirred and ultrasonicated for 3 hours to obtain a reduced graphene oxide organic dispersion with a mass concentration of 40 wt%.

[0037] (2) Polylactic acid powder is added to the above-mentioned reduced graphene oxide organic dispersion (the mass ratio of reduced graphene oxide to polylactic acid powder in the reduced graphene oxide organic dispersion is 10:90). The temperature is raised to 160 °C, stirred and kept warm for 2 hours, then cooled to room temperature at a rate of 5 °C / min. After filtration, it is vacuum-dried to obtain core-shell reduced graphene oxide / polylactic acid composite powder.

[0038] (3) The vacuum-dried reduced graphene oxide / polylactic acid composite powder is added to a single-screw extruder and extruded through the die first zone, the main machine first zone, the main machine second zone, the main machine third zone and the main machine fourth zone in sequence. Set the temperature of the die first zone of the single-screw extruder to 205 °C, the temperature of the main machine first zone to 200 °C, the temperature of the main machine second zone to 205 °C, the temperature of the main machine third zone to 210 °C, the temperature of the main machine fourth zone to 210 °C, the screw rotation and extrusion speed to 8 rpm, control the cooling temperature of the first section to 50 °C, control the cooling temperature of the second section to 40 °C. After extrusion, drawing, cooling and traction, a 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing wire with a diameter of 1.75 ± 0.05 mm is obtained (SEM image is as Figure 1 shown).

[0039] Example 3

[0040] (1) Graphene oxide is added to water to obtain a graphene oxide aqueous dispersion. The graphene oxide aqueous dispersion is freeze-dried to obtain graphene oxide powder, which is further reduced to obtain reduced graphene oxide powder. The reduced graphene oxide powder is added to an ethanol solvent, stirred and ultrasonicated for 3 hours to obtain a reduced graphene oxide organic dispersion with a mass concentration of 40 wt%.

[0041] (2) Polylactic acid powder is added to the above-mentioned reduced graphene oxide organic dispersion (the mass ratio of reduced graphene oxide to polylactic acid powder in the reduced graphene oxide organic dispersion is 8:92). The temperature is raised to 160 °C, stirred and kept warm for 2 hours, then cooled to room temperature at a rate of 5 °C / min. After filtration, it is vacuum-dried to obtain core-shell reduced graphene oxide / polylactic acid composite powder.

[0042] (3) Add the vacuum-dried reduced graphene oxide / polylactic acid composite powder to a single-screw extruder, and let it be extruded successively through the first die zone, the first main machine zone, the second main machine zone, the third main machine zone, and the fourth main machine zone of the die. Set the temperature of the first die zone of the single-screw extruder to 205 °C, the temperature of the first main machine zone to 200 °C, the temperature of the second main machine zone to 205 °C, the temperature of the third main machine zone to 210 °C, and the temperature of the fourth main machine zone to 210 °C. The screw rotation extrusion speed is 8 rpm. Control the cooling temperature of the first stage to 50 °C and the cooling temperature of the second stage to 35 °C. After extrusion, wire drawing, cooling, and traction, a 3D printing reduced graphene oxide / polylactic acid composite absorbing wire with a diameter of 1.75 ± 0.05 mm is obtained.

[0043] Example 4

[0044] (1) Add graphene oxide to water to obtain a graphene oxide aqueous dispersion. Freeze-dry the graphene oxide aqueous dispersion to obtain graphene oxide powder, and further reduce it to obtain reduced graphene oxide powder. Add the reduced graphene oxide powder to an ethanol solvent, stir and ultrasonicate for 3 hours to obtain a reduced graphene oxide organic dispersion with a mass concentration of 60 wt%.

[0045] (2) Add polylactic acid powder to the above-mentioned reduced graphene oxide organic dispersion (the mass ratio of reduced graphene oxide to polylactic acid powder in the reduced graphene oxide organic dispersion is 6:94). Heat up to 180 °C, stir and keep warm for 3 hours, then cool down to room temperature at a rate of 5 °C / min. After filtration, vacuum dry to obtain a core-shell type reduced graphene oxide / polylactic acid composite powder.

[0046] (3) Add the vacuum-dried reduced graphene oxide / polylactic acid composite powder to a single-screw extruder, and let it be extruded successively through the first die zone, the first main machine zone, the second main machine zone, the third main machine zone, and the fourth main machine zone of the die. Set the temperature of the first die zone of the single-screw extruder to 205 °C, the temperature of the first main machine zone to 200 °C, the temperature of the second main machine zone to 205 °C, the temperature of the third main machine zone to 210 °C, and the temperature of the fourth main machine zone to 210 °C. The screw rotation extrusion speed is 10 rpm. Control the cooling temperature of the first stage to 40 °C and the cooling temperature of the second stage to 20 °C. After extrusion, wire drawing, cooling, and traction, a 3D printing reduced graphene oxide / polylactic acid composite absorbing wire with a diameter of 1.75 ± 0.05 mm is obtained (the SEM image is as Figure 2 shown).

[0047] Example 5

[0048] (1) Graphene oxide is added to water to obtain a graphene oxide aqueous dispersion. The graphene oxide aqueous dispersion is freeze-dried to obtain graphene oxide powder, which is further reduced to obtain reduced graphene oxide powder. The reduced graphene oxide powder is added to an ethanol solvent, and stirred and ultrasonicated for 3 hours to obtain a reduced graphene oxide organic dispersion with a mass concentration of 60 wt%.

[0049] (2) Polylactic acid powder is added to the above-mentioned reduced graphene oxide organic dispersion (the mass ratio of reduced graphene oxide to polylactic acid powder in the reduced graphene oxide organic dispersion is 2:98). The temperature is raised to 180 °C, stirred and kept warm for 3 hours, then cooled to room temperature at a rate of 5 °C / min, filtered and vacuum-dried to obtain core-shell reduced graphene oxide / polylactic acid composite powder.

[0050] (3) The vacuum-dried reduced graphene oxide / polylactic acid composite powder is added to a single-screw extruder and extruded successively through the first die zone, the first main machine zone, the second main machine zone, the third main machine zone and the fourth main machine zone. Set the temperature of the first die zone of the single-screw extruder to 205 °C, the temperature of the first main machine zone to 200 °C, the temperature of the second main machine zone to 205 °C, the temperature of the third main machine zone to 210 °C, the temperature of the fourth main machine zone to 210 °C, the screw rotation and extrusion speed to 8 rpm, control the cooling temperature of the first section to 60 °C, control the cooling temperature of the second section to 30 °C, and obtain 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing filaments with a diameter of 1.75 ± 0.05 mm through extrusion, wire drawing, cooling and traction.

[0051] Example 6

[0052] (1) Graphene oxide is added to water to obtain a graphene oxide aqueous dispersion. The graphene oxide aqueous dispersion is freeze-dried to obtain graphene oxide powder, which is further reduced to obtain reduced graphene oxide powder. The reduced graphene oxide powder is added to an ethanol solvent, and stirred and ultrasonicated for 3 hours to obtain a reduced graphene oxide organic dispersion with a mass concentration of 40 wt%.

[0053] (2) Polylactic acid powder is added to the above-mentioned reduced graphene oxide organic dispersion (the mass ratio of reduced graphene oxide to polylactic acid powder in the reduced graphene oxide organic dispersion is 1:99). The temperature is raised to 180 °C, stirred and kept warm for 3 hours, then cooled to room temperature at a rate of 5 °C / min, filtered and vacuum-dried to obtain core-shell reduced graphene oxide / polylactic acid composite powder.

[0054] (3) Add the vacuum-dried reduced graphene oxide / polylactic acid composite powder into a single-screw extruder, and let it be extruded successively through the first die zone, the first main machine zone, the second main machine zone, the third main machine zone, and the fourth main machine zone of the die. Set the temperature of the first die zone of the single-screw extruder to 205 °C, the temperature of the first main machine zone to 200 °C, the temperature of the second main machine zone to 205 °C, the temperature of the third main machine zone to 210 °C, and the temperature of the fourth main machine zone to 210 °C. The screw rotation extrusion speed is 8 rpm. Control the cooling temperature of the first stage to 50 °C and the cooling temperature of the second stage to 40 °C. After extrusion, wire drawing, cooling, and traction, a 3D printed reduced graphene oxide / polylactic acid composite wave-absorbing wire with a diameter of 1.75 ± 0.05 mm is obtained (SEM images are as shown in Figure 3 ).

[0055] Comparative Example 1

[0056] (1) Add graphene and polylactic acid powder into a high-speed mixer at a mass ratio of 8:92 and mix for 60 min to obtain a graphene and polylactic acid mixed powder, and vacuum-dry it for 8 h;

[0057] (2) Add the vacuum-dried graphene and polylactic acid mixed powder into a single-screw extruder, and let it be extruded successively through the first die zone, the first main machine zone, the second main machine zone, the third main machine zone, and the fourth main machine zone of the die. Set the temperature of the first die zone of the single-screw extruder to 205 °C, the temperature of the first main machine zone to 200 °C, the temperature of the second main machine zone to 205 °C, the temperature of the third main machine zone to 210 °C, and the temperature of the fourth main machine zone to 210 °C. The screw rotation extrusion speed is 8 rpm. Control the cooling temperature of the first stage to 50 °C and the cooling temperature of the second stage to 40 °C. After extrusion, wire drawing, cooling, and traction, a graphene / polylactic acid composite wave-absorbing wire with a diameter of 1.75 ± 0.05 mm is obtained.

[0058] Comparative Example 2

[0059] (1) Add graphene oxide into water to obtain a graphene oxide aqueous dispersion, subject the graphene oxide aqueous dispersion to freeze-drying to obtain graphene oxide powder, and further reduce it to obtain reduced graphene oxide powder; add the reduced graphene oxide powder into an ethanol solvent, stir and sonicate for 3 hours to obtain a reduced graphene oxide organic dispersion with a mass concentration of 40 wt%;

[0060] (2) Add polylactic acid powder into the above-mentioned reduced graphene oxide organic dispersion (the mass ratio of reduced graphene oxide to polylactic acid powder in the reduced graphene oxide organic dispersion is 1:99), raise the temperature to 180 °C, stir and keep warm for 3 hours, then cool down to room temperature at a speed of 5 °C / min, filter and vacuum-dry to obtain a core-shell type reduced graphene oxide / polylactic acid composite powder;

[0061] (3) Add the vacuum-dried reduced graphene oxide / polylactic acid composite powder to a single-screw extruder, and let it be extruded successively through the first die zone, the first main machine zone, the second main machine zone, the third main machine zone, and the fourth main machine zone of the die. Set the temperature of the first die zone of the single-screw extruder to 185 °C, the temperature of the first main machine zone to 180 °C, the temperature of the second main machine zone to 230 °C, the temperature of the third main machine zone to 240 °C, and the temperature of the fourth main machine zone to 240 °C. The screw rotation and extrusion speed is 12 rpm. Control the cooling temperature of the first section at 50 °C and the cooling temperature of the second section at 40 °C. After extrusion, wire drawing, cooling, and traction, a reduced graphene oxide / polylactic acid composite wave-absorbing wire with a diameter of 1.75 ± 0.35 mm is obtained.

[0062] Sample analysis

[0063] Print test specimens of the composite wave-absorbing wires prepared in the examples and comparative examples using a 3D printer. Set the printing temperature to 210 °C, the platform temperature to 50 °C, the printing speed to 60 mm / s, and the filling rate to 100%. The tensile test adopts the ISO527-2 / 1A (Determination of Tensile Properties of Plastics) test standard, printed into a dumbbell shape, and the printing direction is 0 degrees; for the bending test standard, the standard adopted is the three-point bending test standard in ISO14125:1998 (Determination of Flexural Properties of Reinforced Plastics Composites). The size of the sample is 80 mm * 10 mm * 4 mm, and the printing direction is 0 degrees; the impact test adopts the standard of ISO 180-2000 (Determination of Impact Strength of Plastics), and the sample size adopted is 80 mm * 10 mm * 4 mm, and the printing direction is 0 degrees; the sample size for testing the reflectivity is 180 mm * 180 mm * 2 mm, and the printing direction is 0 degrees. Test the reflectivity of the flat plate in the frequency bands of 1 - 4 GHz and 4 - 18 GHz. The results are shown in Table 1:

[0064] Table 1 Performance Tests of Composite Wave-Absorbing Wires in Examples and Comparative Examples

[0065]

[0066] The above-described examples have elaborated on the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, supplements, or substitutions in a similar manner within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A preparation method of a 3D printing-reduced graphene oxide / polylactic acid composite wave-absorbing wire material, characterized in that, It includes the following steps: (1) Add graphene oxide into water to obtain a graphene oxide aqueous dispersion. Freeze-dry the graphene oxide aqueous dispersion to obtain graphene oxide powder, and further reduce it to obtain reduced graphene oxide powder. Add the reduced graphene oxide powder into an organic solvent, stir and ultrasonicate to obtain a reduced graphene oxide organic dispersion with a mass concentration of 20-65 wt%; (2) Add polylactic acid powder into the reduced graphene oxide organic dispersion. The mass ratio of reduced graphene oxide to polylactic acid powder in the reduced graphene oxide organic dispersion is 0.01-0.14:

1. Heat up to 140-180 °C, stir and keep warm for 1-3 hours, then cool to room temperature. Filter and vacuum-dry to obtain core-shell reduced graphene oxide / polylactic acid composite powder. The melt index of the polylactic acid powder is 10-16 g / 10 min; (3) The vacuum-dried core-shell reduced graphene oxide / polylactic acid composite powder is extruded, drawn, cooled, and pulled to obtain a 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing filament; In step (3), add the vacuum-dried core-shell reduced graphene oxide / polylactic acid composite powder as the raw material into a single-screw extruder, and make the raw material pass through the first die zone, the first main machine zone, the second main machine zone, the third main machine zone, and the fourth main machine zone for extrusion in sequence. The temperature of the single-screw extruder is set as follows: the temperature of the first die zone is 190-220 °C, the temperature of the first main machine zone is 185-215 °C, the temperature of the second main machine zone is 190-225 °C, the temperature of the third main machine zone is 200-230 °C, and the temperature of the fourth main machine zone is 200-230 °C. The parameter settings for the cooling stage of the single-screw extruder are: control the first-stage cooling temperature at 40-60 °C, and control the second-stage cooling temperature at 20-50 °C.

2. The preparation method of the 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing wire material according to claim 1, characterized in that, The organic solvent includes methanol, ethanol, acetonitrile, formic acid, acetic acid, formamide, or acetamide.

3. The preparation method of the 3D printing-reduced graphene oxide / polylactic acid composite microwave absorbing wire material according to claim 1, wherein, In step (2), the cooling parameter is: the cooling rate is 1-10 °C / min.

4. The preparation method of the 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing wire material according to claim 1, characterized in that, The screw rotation and extrusion speed of the single-screw extruder is 6-10 rpm.

5. A 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing filament prepared by the preparation method of the 3D printing reduced graphene oxide / polylactic acid composite wave-absorbing filament according to any one of claims 1-4.

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