Preparation method of high-toughness wood-plastic composite wire for 3D printing

Abstract

The application discloses a preparation method of high-toughness wood-plastic composite wire for 3D printing, and belongs to the field of wood-plastic composite materials. The application aims at solving the problem that the compatibility of wood fibers and thermoplastic is poor, leading to a rough surface of wood-plastic composite wire and low toughness. The method comprises the following steps: 1, weighing; 2, one-time melt extrusion; 3, two-time melt extrusion; and 4, wire drawing. The application is used for the preparation of high-toughness wood-plastic composite wire for 3D printing.

Description

Technical Field

[0001] This invention belongs to the field of wood-plastic composite materials. Background Technology

[0002] Currently, domestic research on wood-plastic composite consumables for 3D printing mainly focuses on the preparation of composite filaments, using wood fibers and polymers, adding different additives, and performing 3D printing using the fused deposition model.

[0003] However, the addition of wood fibers results in poor compatibility between wood fibers and thermoplastics, leading to a rougher surface and lower toughness in wood-plastic composite filaments. This, in turn, affects the mechanical properties of the material and reduces printing stability, such as uneven material output and filament breakage. For wood-plastic composite filaments, improving the toughness of the filaments can significantly improve the smoothness of the printing process, the structural integrity of the product, its impact resistance, model accuracy, and surface quality. Summary of the Invention

[0004] This invention aims to address the problem that the poor compatibility between existing wood fibers and thermoplastics leads to a rough surface and low toughness in wood-plastic composite filaments, and provides a method for preparing high-toughness wood-plastic composite filaments for 3D printing.

[0005] A method for preparing high-toughness wood-plastic composite filaments for 3D printing, comprising the following steps:

[0006] I. Weighing:

[0007] Weigh out 1 to 30 parts by weight of ethylene-methyl acrylate-glycidyl methacrylate copolymer, 35 to 65 parts of polylactic acid, 10 to 40 parts of wood fiber and 1 to 3 parts of flow modifier.

[0008] II. Single-stage melt extrusion:

[0009] The weighed ethylene-methyl acrylate-glycidyl methacrylate copolymer and polylactic acid were mixed evenly, and then melt-extruded once using a single screw extruder. Finally, the mixture was cooled, crushed and granulated to obtain the blended polymer.

[0010] III. Secondary melt extrusion:

[0011] The weighed wood fibers, flow modifier and blended polymer prepared in step two are mixed evenly, and then a second melt extrusion is performed using a twin-screw extruder. After cooling, crushing and granulation, and finally drying, wood-plastic granules are obtained.

[0012] IV. Wire drawing:

[0013] Wood-plastic composite filaments are drawn into filaments using a single-screw wire drawing machine, followed by water cooling and traction winding to obtain high-toughness wood-plastic composite filaments for 3D printing.

[0014] The beneficial effects of this invention are:

[0015] 1. This invention uses wood flour with a high mesh size to improve the dispersion of wood flour in the plastic matrix. On the other hand, it selects ethylene-methyl acrylate-glycidyl methacrylate copolymer (EMA-GMA) as a toughening agent between wood fibers and polylactic acid, which effectively improves the toughness of the material.

[0016] 2. This invention improves the compatibility and melt flow of wood-plastic composite filaments through a secondary granulation process, balancing cost-effectiveness and toughness to enhance printability. During the primary granulation, the melting temperature of PLA and EMA-GMA is set between 120℃ and 230℃ to allow the epoxy groups in glycidyl methacrylate to react with the hydroxyl and carboxyl groups in the PLA molecular chain, forming cross-links. In the secondary granulation, EMA-GMA acts as a toughening agent and compatibilizer, transferring and dispersing stress under external forces, reducing crack initiation and propagation, and improving the overall toughness of the material.

[0017] 3. The filament produced by this invention possesses the natural feel of wood, is dimensionally stable, has a smooth surface, and requires minimal processing conditions. Furthermore, the printed products do not warp or clog, and exhibit a certain degree of toughness, meeting the needs of 3D printing. The printed products have excellent physical and mechanical properties, strong weather resistance, and conform to green environmental protection principles, while also saving costs to a certain extent for materials or products.

[0018] The method for preparing high-toughness wood-plastic composite filaments for 3D printing provided by this invention has the advantages of simple preparation, low cost and good toughness, and provides a new idea for expanding the application scenarios of wood-plastic composite filaments. Attached Figure Description

[0019] Figure 1 A photograph of the high-toughness wood-plastic composite wire prepared in Example 1;

[0020] Figure 2 This is a picture of the sample after 3D printing using high-toughness wood-plastic composite filament in Example 4. Detailed Implementation

[0021] Specific Implementation Method 1: This implementation method provides a method for preparing high-toughness wood-plastic composite filaments for 3D printing, which is carried out according to the following steps:

[0022] I. Weighing:

[0023] Weigh out 1 to 30 parts by weight of ethylene-methyl acrylate-glycidyl methacrylate copolymer, 35 to 65 parts of polylactic acid, 10 to 40 parts of wood fiber and 1 to 3 parts of flow modifier.

[0024] II. Single-stage melt extrusion:

[0025] The weighed ethylene-methyl acrylate-glycidyl methacrylate copolymer and polylactic acid were mixed evenly, and then melt-extruded once using a single screw extruder. Finally, the mixture was cooled, crushed and granulated to obtain the blended polymer.

[0026] III. Secondary melt extrusion:

[0027] The weighed wood fibers, flow modifier and blended polymer prepared in step two are mixed evenly, and then a second melt extrusion is performed using a twin-screw extruder. After cooling, crushing and granulation, and finally drying, wood-plastic granules are obtained.

[0028] IV. Wire drawing:

[0029] Wood-plastic composite filaments are drawn into filaments using a single-screw wire drawing machine, followed by water cooling and traction winding to obtain high-toughness wood-plastic composite filaments for 3D printing.

[0030] The beneficial effects of this embodiment are:

[0031] 1. This embodiment uses wood flour with a high mesh size to improve the dispersion of wood flour in the plastic matrix. On the other hand, ethylene-methyl acrylate-glycidyl methacrylate copolymer (EMA-GMA) is selected as a toughening agent between wood fiber and polylactic acid to effectively improve the toughness of the material.

[0032] 2. This embodiment improves the compatibility and melt flow of wood-plastic composite filaments through secondary granulation, balancing cost-effectiveness and toughness to enhance printability. During primary granulation, the melting temperature of PLA and EMA-GMA is set between 120℃ and 230℃ to allow the epoxy groups in glycidyl methacrylate to react with the hydroxyl and carboxyl groups in the PLA molecular chain, forming cross-links. In secondary granulation, EMA-GMA acts as a toughening agent and compatibilizer, transferring and dispersing stress under external forces, reducing crack initiation and propagation, and improving the overall toughness of the material.

[0033] 3. The filament produced in this embodiment possesses the natural feel of wood, is dimensionally stable, has a smooth surface, and requires minimal processing conditions. Furthermore, the printed products do not warp or clog, and exhibit a certain degree of toughness, meeting the demands of 3D printing. The printed products have excellent physical and mechanical properties, strong weather resistance, and conform to green and environmentally friendly principles, while also saving costs to a certain extent for materials or products.

[0034] The method for preparing high-toughness wood-plastic composite filaments for 3D printing provided in this embodiment has advantages such as simple preparation, low cost, and good toughness, and provides a new idea for expanding the application scenarios of wood-plastic composite filaments.

[0035] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mass percentage of glycidyl methacrylate monomer in the ethylene-methyl acrylate-glycidyl methacrylate copolymer described in step one is 1% to 8%. Everything else is the same as in Specific Implementation Method One.

[0036] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the polylactic acid described in step one, under the conditions of a temperature of 210℃ and a load of 2.16kg, has a melt flow rate of 3g / 10min to 10g / 10min. Everything else is the same as in Specific Implementation Method One or Two.

[0037] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the wood fiber mentioned in step one is one or a mixture of several of the following: wood flour, rice husk flour, bamboo flour, straw flour, fruit shell flour, and sugarcane bagasse; the mesh size of the wood fiber mentioned in step one is 60 mesh to 200 mesh. Everything else is the same as in Specific Implementation Methods One to Three.

[0038] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the flowability modifier mentioned in step one is one or a mixture of several of the following: polyethylene wax, polypropylene wax, paraffin wax, stearic acid, zinc stearate, and calcium stearate. Everything else is the same as in Specific Implementation Methods One to Four.

[0039] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the moisture content of the ethylene-methyl acrylate-glycidyl methacrylate copolymer, polylactic acid, and wood fiber mentioned in step one is all below 3%. Everything else is the same as in Specific Implementation Methods One to Five.

[0040] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: in step two, a high-speed mixer is used to mix the weighed ethylene-methyl acrylate-glycidyl methacrylate copolymer and polylactic acid for 3 to 8 minutes at a speed of 1000 to 1500 rpm. Then, a single-screw extruder is used to melt-extrude the mixture in one pass at a temperature of 120°C to 230°C and a main extruder speed of 10 to 20 rpm. Finally, the mixture is cooled, crushed, and granulated to a particle size of 2 mm to 8 mm to obtain the blended polymer. Everything else is the same as in Specific Implementation Methods One to Six.

[0041] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: in step three, a high-speed mixer is used to mix the weighed wood fibers, flow modifier, and the blended polymer prepared in step two for 3 to 8 minutes at a speed of 1000 to 1500 rpm. Then, a twin-screw extruder is used for secondary melt extrusion at a temperature of 140°C to 200°C and a main extruder speed of 30 to 60 rpm. After cooling, crushing, and granulation to a particle size of 2 mm to 8 mm, the mixture is finally dried to a moisture content of <2% to obtain wood-plastic granules. The rest is the same as in Specific Implementation Methods One to Seven.

[0042] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that, in step four, the wood-plastic composite pellets are drawn into fibers using a single-screw wire drawing machine under the conditions of a temperature of 110℃~170℃, a main engine speed of 15Hz~25Hz, and a traction speed of 10rpm~20rpm. Everything else is the same as in Specific Implementation Methods One to Eight.

[0043] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One through Nine in the following ways: Step Two utilizes a single-screw extruder for a single-stage melt extrusion at two temperature zones of 130°C and 220°C, with the main extruder rotating at 10 rpm to 20 rpm. Step Three utilizes a twin-screw extruder for a second-stage melt extrusion at seven temperature zones of 150°C, 160°C, 170°C, 180°C, 170°C, 160°C, and 150°C, with the main extruder rotating at 30 rpm to 60 rpm. In Step Four, a single-screw wire drawing machine is used to draw the wood-plastic composite pellets into fibers at two temperature zones of 165°C and 125°C, with the main extruder rotating at 15 Hz to 25 Hz and the traction speed at 10 rpm to 20 rpm. The rest is the same as in Specific Implementation Methods One through Nine.

[0044] The beneficial effects of the present invention are verified using the following embodiments:

[0045] Example 1:

[0046] A method for preparing high-toughness wood-plastic composite filaments for 3D printing, comprising the following steps:

[0047] I. Weighing:

[0048] Weigh out 10 parts by weight of ethylene-methyl acrylate-glycidyl methacrylate copolymer (EMA-GMA), 58 parts of polylactic acid (PLA), 30 parts of wood fiber and 2 parts of flow modifier.

[0049] The mass percentage of glycidyl methacrylate monomer in the ethylene-methyl acrylate-glycidyl methacrylate copolymer is 8%.

[0050] The polylactic acid described herein has a melt flow rate of 7 g / 10 min at a temperature of 210 °C and a load of 2.16 kg.

[0051] The wood fiber is wood flour; the mesh size of the wood fiber is 120 mesh to 150 mesh.

[0052] The fluidity modifier is polyethylene wax;

[0053] The ethylene-methyl acrylate-glycidyl methacrylate copolymer and polylactic acid, after being dried at 60°C for 6 hours, both had a moisture content of less than 3%.

[0054] The wood fibers were dried at 103°C until the moisture content was all below 3%.

[0055] II. Single-stage melt extrusion:

[0056] Using a high-speed mixer, at a speed of 1500 rpm, the weighed ethylene-methyl acrylate-glycidyl methacrylate copolymer and polylactic acid were mixed for 5 minutes. Then, using a single-screw extruder, the mixture was melt-extruded in one step at a temperature of 130°C in temperature zone one, 220°C in temperature zone two, and a main extruder speed of 15 rpm. Finally, the mixture was cooled, crushed, and granulated to a particle size of 2 mm to 8 mm to obtain the blended polymer.

[0057] III. Secondary melt extrusion:

[0058] Using a high-speed mixer, at a speed of 1500 rpm, the weighed wood fibers, flow modifier and the blended polymer prepared in step two were mixed for 5 minutes. Then, using a twin-screw extruder, the mixture was melt-extruded twice at temperatures of 150℃, 160℃, 170℃, 180℃, 170℃, 160℃ and 150℃ in temperature zones one to seven, respectively, and the main extruder speed was 40 rpm. The mixture was then cooled, crushed and granulated to a particle size of 2 mm to 8 mm, and finally dried to a moisture content of <2% to obtain wood-plastic granules.

[0059] IV. Wire drawing:

[0060] Under the conditions of temperature zone 1 of 165℃, temperature zone 2 of 125℃, main machine speed of 20Hz and traction speed of 15rpm, wood-plastic composite particles are drawn into fibers using a single screw wire drawing machine, followed by water cooling and traction winding to obtain high-toughness wood-plastic composite wire; the diameter of the high-toughness wood-plastic composite wire is 1.75±5mm.

[0061] Example 2: This example differs from Example 1 in that, in step 1, 20 parts by weight of ethylene-methyl acrylate-glycidyl methacrylate copolymer (EMA-GMA), 48 parts by weight of polylactic acid (PLA), 30 parts by weight of wood fiber, and 2 parts by weight of flow modifier are weighed. Everything else is the same as in Example 1.

[0062] Example 3: This example differs from Example 1 in that, in step 1, 30 parts by weight of ethylene-methyl acrylate-glycidyl methacrylate copolymer (EMA-GMA), 38 parts by weight of polylactic acid (PLA), 30 parts by weight of wood fiber, and 2 parts by weight of flow modifier are weighed. Everything else is the same as in Example 1.

[0063] Comparative Experiment: This comparative experiment differs from Example 1 in that: the use of ethylene-methyl acrylate-glycidyl methacrylate copolymer is omitted; in step one, 68 parts by weight of polylactic acid (PLA), 30 parts by weight of wood fiber, and 2 parts by weight of flow modifier are weighed; step two is omitted. Everything else is the same as in Example 1.

[0064] The wood-plastic pellets prepared in Examples 1 to 3 and Comparative Experiment Step 3 were hot-pressed to obtain mechanical test specimens. Bending tests were performed according to ASTM D 790-10, tensile property tests according to ASTM D 638-14, and impact strength tests according to ASTM D 6110. The test results are shown in Table 1 below.

[0065] Table 1

[0066] category Example 1 Example 2 Example 3 Comparative experiment Bending strength / MPa 21.06 18.84 16.28 46.98 Tensile strength / MPa 8.16 17.98 8.98 27.01 Elongation at break / % 4.56 2.31 2.62 4.50 <![CDATA[Impact strength / kJ·m -2 > 8.00 14.63 17.80 5.71

[0067] As shown in the table, the examples use wood flour as a filler for the thermoplastic filaments, which on the one hand gives the material a natural wood-like feel, and on the other hand reduces the material cost. The selection of ethylene-methyl acrylate-glycidyl methacrylate copolymer (EMA-GMA) as a toughening agent between the wood fibers and polylactic acid effectively improves the impact strength of the composite material. Compared with the comparative experiment, the impact strength increased by 211.7%, and the toughness was also improved, making it possible to print wood fiber / polymer composite products with good performance or special functions.

[0068] Figure 1 The image shows a physical picture of the high-toughness wood-plastic composite wire prepared in Example 1. As can be seen from the picture, the high-toughness wood-plastic composite wire prepared in the example has stable dimensions and a smooth surface.

[0069] Example 4:

[0070] The high-toughness wood-plastic composite filament prepared in Example 1 was used for 3D printing, and the specific method is as follows:

[0071] The Cure model was used to output an STL file, and the 3D model was sliced ​​using Bamboo Studio software to obtain a G.code file. Before printing, the high-toughness wood-plastic composite filament was dried in a forced-air drying oven at 60°C. After drying, it was printed using a fused deposition model 3D printer, specifically the Tuozhu X1 model. The printing conditions were set as shown in Table 2, resulting in a 3D-printed sample using the high-toughness wood-plastic composite filament.

[0072] Table 2

[0073] Printing platform temperature 35℃ Print nozzle temperature 210℃ Print layer height 0.12mm Printing speed First floor: 50mm / s; Exterior wall: 200mm / s; Interior wall: 300mm / s Sparse Fill 15％ heated bed bonding Brim 1st Floor

[0074] Figure 2 The image shows a sample 3D printed using high-toughness wood-plastic composite filament in Example 4. As can be seen from the image, the sample has a good shape, stable dimensions, no warping, and smooth edges, indicating good application prospects.

Claims

1. A method for preparing high-tenacity wood-plastic composite wire for 3D printing, characterized by It is carried out in the following steps: I. Take: Take 10 parts~30 parts of ethylene-methyl acrylate-glycidyl methacrylate copolymer, 38 parts~58 parts of polylactic acid, 30 parts of wood fiber and 2 parts of flowability modifier according to the mass fraction; The mass percentage of glycidyl methacrylate monomer in the ethylene-methyl acrylate-glycidyl methacrylate copolymer is 8%; The melt mass flow rate of the polylactic acid is 7g / 10min under the condition of temperature 210℃ and load 2.16kg; The wood fiber is wood powder; The mesh number of the wood fiber is 120 mesh~150 mesh; The flowability modifier is polyethylene wax; The ethylene-methyl acrylate-glycidyl methacrylate copolymer and polylactic acid are dried at a temperature of 60℃ for 6h, and the water content is below 3%; The wood fiber is dried at a temperature of 103℃ until the water content is below 3%; II. Once melt extrusion: Use a high-speed mixer to mix the weighed ethylene-methyl acrylate-glycidyl methacrylate copolymer and polylactic acid at a speed of 1500rmp for 5min, then use a single screw extruder to melt extrude once under the condition of temperature zone one temperature 130℃, temperature zone two temperature 220℃ and main machine speed 15rmp, finally cool and crush to particle size 2mm~8mm to obtain a blended polymer; III. Twice melt extrusion: Use a high-speed mixer to mix the weighed wood fiber, flowability modifier and blended polymer prepared in step II at a speed of 1500rmp for 5min, then use a double screw extruder to melt extrude twice under the condition of temperature zone one to seven temperatures of 150℃, 160℃, 170℃, 180℃, 170℃, 160℃ and 150℃ respectively, and main machine speed 40rmp, cool and crush to particle size 2mm~8mm, finally dry to water content <2% to obtain wood-plastic granules; IV. Wire drawing: Use a single screw wire drawing machine to draw the wood-plastic granules under the condition of temperature zone one temperature 165℃, temperature zone two temperature 125℃, main machine speed 20Hz and pulling speed 15rmp, then water cooling and traction winding to obtain high-toughness wood-plastic composite wire.

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