A method for preparing FDM 3D printed parts with high electrical conductivity

Abstract

The present invention relates to a method for preparing a high-conductivity FDM 3D printed part. On the basis of the FDM 3D printed part, 3D printing is combined with ultrasound and microwave treatment, and ultrasound is used to make the conductive carbon material evenly adhere to the surface of the 3D printed part. Then, the sample is subjected to microwave treatment using the strong effect of the carbon material and microwave radiation, so that the carbon material attached to the surface of the part is embedded in the polymer matrix, and the conductive filler particles are concentrated on the surface of the printed part, so that the surface of the part is functionalized, and a conductive network is constructed on the surface of the part, while maintaining the excellent mechanical properties of the polymer matrix itself. The FDM 3D printed part obtained by the present invention after microwave radiation treatment does not deteriorate the mechanical properties of the polymer body, effectively solves the problem of decreased mechanical properties of the printed part due to the addition of fillers, and simplifies the complicated preparation process of the composite wire, which is helpful to promote the application of FDM 3D printing in the field of conductive functional devices.

Description

Technical Field

[0001] The invention belongs to the field of additive manufacturing, and specifically relates to a method for preparing a high-conductivity FDM 3D printed part. Background Art

[0002] Nowadays, with the rapid development of the computer and artificial intelligence industries, the market demand for materials with ideal conductive properties is increasing. 3D printing technology, as a new preparation method, has begun to be applied in various industries, including the electronics industry. Fused deposition modeling (FDM) 3D printing is one of the most common and simplest 3D printing technologies. Conductive parts prepared by printing with conductive wires have the potential to be used in conductive electrodes, sensors, wearable devices and other fields.

[0003] To prepare conductive wires for FDM 3D printing, polymers and conductive fillers (metal powders, conductive carbon materials, etc.) need to be melt-blended and extruded through a twin-screw extruder to prepare conductive wires, and then the conductive wires are melt-extruded through a printer to print out conductive parts. This blending method takes a long time to prepare conductive wires, and the electrical properties of samples prepared with this composite wire are mainly based on the amount of conductive filler added. When the amount of conductive filler exceeds the percolation threshold, a conductive network is formed in the polymer composite material, and a highly conductive wire can be obtained. However, the addition of too much conductive filler will deteriorate the mechanical properties of the polymer matrix itself, making the FDM3D printed parts brittle. At the same time, too much filler load can easily clog the printer nozzle, making the printing process difficult.

[0004] Microwave technology is a process in which a high-frequency electromagnetic field is generated between electromagnetic waves with an average wavelength of 0.1m and 1m. Objects absorb microwaves, internal molecules rearrange themselves, and electromagnetic energy is converted into thermal energy, causing the material to heat up rapidly.

[0005] Chinese patent document CN202011097290.8 discloses a method of using microwave treatment to improve the tensile and folding resistance of FDM 3D printed TPU shoe materials. This method uses microwaves to irradiate polyurethane or polyurethane composites to improve the interlayer bonding performance of 3D printed parts.

[0006] Chinese patent document CN201910128191.2 discloses a hybrid manufacturing technology based on fused deposition modeling 3D printing. On the basis of preparing the conductive material body, heat-expandable microspheres modified by carbon nanotube adhesion are introduced during the printing process. After post-printing heat treatment, the overall conductive performance of the printed part is further improved.

[0007] Chinese patent document CN106313787A discloses a three-layer composite wire, which consists of a plastic layer, a metal layer, and a packaging layer from the inside to the outside. The metal layer introduced in this way can be suitable for printing functional devices that require electrical conductivity, maintaining the mechanical printing performance of plastic 3D printing and achieving the conductive function.

[0008] However, among the currently disclosed patents, most of them use the method of preparing composite wires to obtain conductive 3D printed parts. There are almost no reports on the method of using microwaves to enrich conductive fillers on the surface of parts to prepare highly conductive 3D printed parts. This method can maintain the excellent mechanical properties of the polymer matrix while eliminating the complicated preparation process of composite wires, which plays an important role in expanding the application of 3D printing in the field of conductive functional devices. Summary of the invention

[0009] The purpose of the present invention is to change the limitation of the existing FDM process that wire blending modification is difficult to improve the conductive performance of the printed part, and provide a method for preparing FDM 3D printed parts with high conductive performance. By utilizing the strong effect of carbon materials and microwave radiation, rapid heating and local heating can be achieved. The conductive carbon material on the outer layer of the part is locally heated by microwave radiation, the polymer surface is melted, and the carbon material is embedded to form a conductive composite layer on the outer layer of the printed part. This method is simple to operate, can avoid the cumbersome preparation of composite wires, and promote the application of FDM 3D printing in the field of conductive functional devices.

[0010] To achieve the above objectives, the technical solution of the present invention is: a method for preparing a highly conductive part by FDM 3D printing, which is divided into three steps: 1) using an FDM 3D machine to print the required part; 2) preparing conductive ink and using ultrasonic treatment to attach the conductive filler to the surface of the part; 3) microwave heat treatment.

[0011] The preparation of the parts required for the FDM 3D printing machine is as follows: using commercial wires (thermoplastic polymer wires such as ABS, PLA, TPU, etc.) to print out the required 3D model according to a given CAD model.

[0012] Preparation of the conductive ink: The conductive filler is a conductive carbon material (one or a combination of carbon nanotubes, graphene, carbon quantum dots, conductive graphite, carbon black, vapor-grown carbon fibers), with a content of 2.5-10 mg / ml. A certain amount of conductive carbon material is weighed and dispersed in an ethanol solution in proportion, and PVP is added in a ratio of carbon material: polyvinyl pyrrolidone (PVP) = 5:1 to ensure the dispersion stability of the carbon material. The mixed solution is ultrasonically treated for 2 hours, and the strong crushing and dispersion effect generated by ultrasonic cavitation is used to ensure the uniform dispersion of the carbon material.

[0013] The surface attachment of the conductive filler is to immerse the printed 3D model in the above conductive ink and perform ultrasonic treatment for 2 hours. The ultrasonic cavitation produces a strong impact force, which evenly disperses the conductive carbon material and attaches it to the surface of the 3D printed part. After the ultrasonic treatment, the 3D model is taken out and placed on a clean glass plate, and the sample is placed in an oven at 40°C and dried for 24 hours.

[0014] The microwave heat treatment is as follows: placing the 3D printed part into a microwave oven, selecting a microwave power of 100-900w, and selecting a microwave treatment time of 10s-60s.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The main advantage of the novel hybrid technology based on fused deposition modeling (FDM) 3D printing of the present invention is that a conductive composite layer is constructed on the surface of a non-conductive 3D printed part by microwave assistance, and a conductive network is formed on the outermost layer of the part without damaging the mechanical properties of the polymer matrix. Specifically, the present invention uniformly adheres conductive carbon materials to the surface of FDM 3D printed parts through ultrasonic treatment, introduces microwave heating, and utilizes the strong effect of carbon materials on microwave radiation to achieve local heating of the surface, embeds the conductive carbon materials into the polymer matrix, and realizes the conductive functionalization of insulating parts. This operation greatly simplifies the 3D printing process of conductive devices based on the preparation of composite wires, saves a lot of time, and avoids the influence of the introduction of fillers on the mechanical properties of the polymer matrix, which helps to promote the application of FDM 3D printing in the field of conductive functional devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the SEM image of the 3D printed part after microwave treatment;

[0017] Figure 2 This is an optical photograph of the cross section of the workpiece after microwave treatment. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0019] The present invention provides a method for FDM 3D printing parts with high conductivity while maintaining the excellent mechanical properties of the polymer itself. The method mainly uses a treatment method combining ultrasonic treatment and microwave treatment to form a conductive functional layer on the outermost layer of the non-conductive polymer matrix. Furthermore, on the basis of conventional printed 3D parts, the present invention uses ultrasonic treatment to evenly distribute the conductive filler on the surface of the printed part, and further uses microwave treatment after drying, utilizing the carbon material's absorption of microwaves to locally generate a large amount of heat, so that the conductive filler is embedded in the surface of the 3D printed part to establish a stable and interconnected conductive network. The 3D printed parts with high conductivity prepared in this way can give the parts excellent conductive properties without degrading the mechanical properties of the parts.

[0020] The following are specific implementation examples of the present invention.

[0021] Embodiment 1

[0022] In the first step, 80A, 1.75mm diameter TPU wire was used to print the sample. The sample layer height was set to 0.4mm, the nozzle diameter was 0.6mm, the wire extrusion ratio was 1.1, the printer nozzle temperature was 210℃, the platform temperature was 50℃, and the printing speed was set to 10mm / s.

[0023] The second step is to prepare conductive ink, using multi-walled carbon nanotubes as conductive fillers, weighing 0.625g of carbon nanotubes and 0.125g of polyvinyl pyrrolidone and dispersing them in 250ml of 95% ethanol solution, at room temperature, magnetic stirring for 30min and then ultrasonic treatment for 2h to obtain uniformly dispersed conductive ink.

[0024] The third step is to place the printed part in conductive ink, ultrasonically treat it for 2 hours, place the treated part on a clean glass plate, and dry it in an oven at 40°C for 24 hours to obtain a 3D printed part with carbon nanotubes attached to the surface.

[0025] In the fourth step, the microwave oven power is set to 500W and the time is set to 10s, and the product obtained in the third step is microwaved for 10s.

[0026] Mechanical properties test

[0027] According to the standard GB / T 1040.1~1040.5-2008, a dumbbell-shaped printing model was set, the tensile specimen size was 50mm×5mm×0.75mm, and the specimen was treated according to the process of Example 1 for testing. A universal testing machine (AGX-100plus, Shimadzu, Japan) was used for the experiment. The elongation at break of the conductive 3D printed part prepared in Example 1 was measured to be 400%, and the tensile strength was 7MPa, which was equivalent to the tensile performance of the untreated pure TPU printed sample.

[0028] Electrical performance test

[0029] The printed strip is set to be a rectangular strip of 50 mm × 8.5 mm × 2 mm. A digital multimeter (RIGOL, DM3068, China) is used to test the resistance of the sample prepared in Example 1 and calculate the conductivity of the sample. The resistance of the sample is measured ten times and the average resistance is 9.08 KΩ. According to the conductivity formula Where R is the ohmic resistance, L is the length, and A is the cross-sectional area. The conductivity of the sample is calculated to be 0.36S / m.

[0030] Embodiment 2

[0031] In the first step, a PCL wire with a wire diameter of 1.75 mm was used to print the sample. The sample layer height was set to 0.2 mm, the nozzle diameter was 0.4 mm, the wire extrusion ratio was 1.0, the printer nozzle temperature was 110°C, the platform temperature was 30°C, and the printing speed was set to 30 mm / s.

[0032] The second step is to prepare conductive ink, using multi-walled carbon nanotubes and graphene as conductive fillers, weighing 0.625g of carbon nanotubes / graphene and 0.125g of polyvinyl pyrrolidone and dispersing them in 250ml of 95% ethanol solution, and at room temperature, magnetic stirring for 30min and then ultrasonic treatment for 2h to obtain uniformly dispersed conductive ink.

[0033] The third step is to place the printed part in conductive ink, ultrasonically treat it for 2 hours, place the treated part on a clean glass plate, and dry it in an oven at 40°C for 24 hours to obtain a 3D printed part with carbon nanotubes attached to the surface.

[0034] In the fourth step, the microwave oven power is set to 900W and the time is set to 5s, and the product obtained in the third step is microwaved for 5s.

[0035] Mechanical properties test

[0036] According to the standard GB / T 1040.1~1040.5-2008, a dumbbell-shaped printing model was set, the tensile specimen size was 50mm×5mm×0.75mm, and the specimen was treated according to the process of Example 2 for testing. The experiment was conducted using a universal testing machine (AGX-100plus, Shimadzu, Japan). The elongation at break of the conductive 3D printed part prepared in Example 2 was measured to be 780%, and the tensile strength was 7.6MPa, which was comparable to the tensile properties of the untreated pure PCL printed sample.

[0037] Electrical performance test

[0038] The printed strip is set to be a rectangular strip of 50 mm × 8.5 mm × 2 mm. A digital multimeter (RIGOL, DM3068, China) is used to test the resistance of the sample prepared in Example 2 and calculate the conductivity of the sample. The resistance of the sample is measured ten times and the average resistance is 8.21 KΩ. According to the conductivity formula Where R is the ohmic resistance, L is the length, and A is the cross-sectional area. The conductivity of the sample is calculated to be 0.36S / m.

[0039] Embodiment 3

[0040] In the first step, a PLA filament with a wire diameter of 1.75 mm was used to print the sample. The sample layer height was set to 0.2 mm, the nozzle diameter was 0.4 mm, the filament extrusion ratio was 1.0, the printer nozzle temperature was 200 ° C, the platform temperature was 40 ° C, and the printing speed was set to 50 mm / s.

[0041] The second step is to prepare conductive ink, using multi-walled carbon nanotubes / graphene / carbon fibers as conductive fillers, weighing 0.625g of carbon nanotubes and 0.125g of polyvinyl pyrrolidone and dispersing them in 250ml of 95% ethanol solution, at room temperature, magnetically stirring for 30min and then ultrasonically treating for 2h to obtain uniformly dispersed conductive ink.

[0042] The third step is to place the printed part in conductive ink, ultrasonically treat it for 2 hours, place the treated part on a clean glass plate, and dry it in an oven at 40°C for 24 hours to obtain a 3D printed part with carbon nanotubes attached to the surface.

[0043] In the fourth step, the microwave oven power is set to 900W and the time is set to 10s, and the product obtained in the third step is microwaved for 10s.

[0044] Mechanical properties test

[0045] According to the standard GB / T 1040.1~1040.5-2008, a dumbbell-shaped printing model was set, the tensile specimen size was 50mm×5mm×0.75mm, and the specimen was treated according to the process of Example 3 for testing. The experiment was conducted using a universal testing machine (AGX-100plus, Shimadzu, Japan). The elongation at break of the conductive 3D printed part prepared in Example 3 was measured to be 4%, and the tensile strength was 51MPa, which was comparable to the tensile properties of the untreated pure PLA printed sample.

[0046] Electrical performance test

[0047] The printed strip is set to be a rectangular strip of 50 mm × 8.5 mm × 2 mm. A digital multimeter (RIGOL, DM3068, China) is used to test the resistance of the sample prepared in Example 3 and calculate the conductivity of the sample. The resistance of the sample is measured ten times and the average resistance is 7.56 KΩ. According to the conductivity formula Where R is the ohmic resistance, L is the length, and A is the cross-sectional area. The conductivity of the sample is calculated to be 0.39 S / m.

[0048] The above are preferred embodiments of the present invention. Any changes made according to the technical solution of the present invention, as long as the resulting functions do not exceed the scope of the technical solution of the present invention, belong to the protection scope of the present invention.

Claims

1. A method for preparing a high-conductivity FDM 3D printed part, characterized in that: The method is applied to 3D printing of conductive devices based on the preparation of composite wires, and the FDM 3D printed parts are subjected to ultrasonic and microwave radiation treatment, specifically: the FDM 3D printed parts are immersed in conductive ink and ultrasonically treated so that the surface of the FDM 3D printed parts is loaded with conductive carbon material. After the ultrasonic treatment, the FDM 3D printed parts are dried, and then the FDM 3D printed parts are subjected to microwave radiation treatment; the conductive filler of the conductive ink is one or a combination of conductive carbon materials including carbon nanotubes, graphene, carbon quantum dots, conductive graphite, carbon black, and vapor-grown carbon fibers, and the content is 2.5-10 mg / ml; polar solvents and surfactants are used to assist in the uniform dispersion of the conductive carbon material.

2. The method for preparing a high-conductivity FDM 3D printed part according to claim 1, characterized in that: The polar solvent uses alcohol as a dispersant.

3. The method for preparing a high-conductivity FDM 3D printed part according to claim 1, characterized in that: The surfactant is a non-ionic polymer compound.

4. The method for preparing a high-conductivity FDM 3D printed part according to claim 1, characterized in that: The power of the microwave radiation is selected to be 100-900W, and the time of the microwave radiation is 10s-60s.

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