A low anisotropy short fiber reinforced PEEK 3D printing filament and its preparation method

Abstract

The application discloses a kind of low anisotropy short fiber reinforced PEEK 3D printing wire and preparation method thereof, the printing wire includes the following components by weight percentage: PEEK resin: 75-90 wt%;Short fiber reinforcement: 10-25 wt%;Interface compatibilizer PEI or coupling agent KH550: 0-3 wt%;Antioxidant or heat stabilizer: 0-1 wt%;Beneficial effect is, the present application starts from fiber space structure regulation, realizes the significant reduction of mechanical property anisotropy of short fiber reinforced PEEK material in 3D printing application by multistage synergic control, while giving consideration to the demand of high strength, high stability and industrial production.

Description

Technical Field

[0001] This invention relates to the field of PEEK 3D printing filament technology, and in particular to a low anisotropy short fiber reinforced PEEK 3D printing filament and its preparation method. Background Technology

[0002] Polyetheretherketone (PEEK) is a high-performance semi-crystalline engineering plastic with excellent high-temperature resistance, corrosion resistance, and mechanical properties, making it widely used in aerospace, medical devices, and high-end equipment. With the development of fused deposition modeling (FDM / FFF) 3D printing technology, PEEK is gradually becoming an important candidate material for high-end 3D printed structural components. To further improve its rigidity and load-bearing capacity, short carbon fibers or short glass fibers are often added to the PEEK matrix to prepare reinforced composite materials for manufacturing high-strength, lightweight functional components. However, in practical 3D printing applications, short-fiber reinforced PEEK materials generally have the following problems: 1. Melt flow leads to high fiber orientation; During the extrusion of reinforced PEEK melt, the melt undergoes significant shear and stretch flow in the screw conveyor, die flow channel and printing nozzle. Since the aspect ratio of short fibers is usually large, they are prone to orientation and alignment along the flow direction under the action of shear field. 2. The mechanical properties of printed components are severely anisotropic; due to the high orientation of fibers in the XY plane, the printed parts have high tensile strength and modulus in the XY direction, but lack effective fiber reinforcement in the Z direction (interlayer direction), resulting in low interlayer bonding strength. 3. Fiber length reduction; In the twin-screw compounding process, if the shear strength is not properly controlled, short fibers are prone to breakage, resulting in a significant decrease in average length. Existing technologies often focus on dispersion uniformity while neglecting the impact of fiber length retention rate on the final printing performance. IV. Secondary orientation during traction and cooling: After wire extrusion, if tension is not properly controlled during traction, cooling and winding, the wire may undergo tensile orientation, which further enhances the axial alignment of the fibers. V. Limitations of existing technologies: Existing technologies for reinforcing PEEK wires are mostly focused on melt stability control, crystallization rate adjustment, wire diameter accuracy control, and printing process window optimization. Few technologies systematically regulate the spatial orientation evolution mechanism of fibers throughout the entire material processing process at the structural level. Therefore, existing short-fiber reinforced PEEK 3D printing materials still suffer from the following problems: highly anisotropic mechanical properties of printed components; significantly insufficient strength in the Z-axis direction; brittle fracture easily occurs between layers; fiber length retention rate is uncontrollable; and fiber orientation structure is not adjustable. The aforementioned issues limit the further application of reinforced PEEK materials in high-load-bearing 3D printing. Based on the above problems, the purpose of this invention is to provide a method for preparing reinforced PEEK printed components by controlling the fiber length retention rate, the perturbation flow field structure design, and the low-tension traction locking technology to systematically regulate the fiber spatial distribution structure. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a low-anisotropy short-fiber reinforced PEEK 3D printing filament, comprising the following components by weight percentage: PEEK resin: 75–90 wt%; short-fiber reinforcement: 10–25 wt%; interface compatibilizer PEI or coupling agent KH550: 0–3 wt%; antioxidant or heat stabilizer: 0–1 wt%.

[0004] As a further supplement to this technical solution, the PEEK is a semi-crystalline polyether ether ketone with a melting point of 330–350℃.

[0005] As a further supplement to this technical solution, the short fiber reinforcement is short carbon fiber or short glass fiber.

[0006] As a further supplement to this technical solution, the initial length of the short fiber reinforcement is 0.2–1.0 mm.

[0007] As a further supplement to this technical solution, the aspect ratio of the short fiber reinforcement is 10–100.

[0008] A method for preparing low anisotropy short fiber reinforced PEEK 3D printing filament includes the following steps: Step (1): PEEK fiber-reinforced dispersion and granulation; Step (2), Reinforced PEEK wire extrusion; Step (3), low-tension floating traction system; Step (4): Rapid quenching and shaping.

[0009] To further supplement this technical solution, step (1) adopts a parallel co-rotating twin-screw extruder with parameters L / D=40-52, screw diameter: 25-50mm, and a zoned temperature control system. PEEK resin is added through the main hopper, and short fibers are added in the rear section of the melting zone through the side feed port. The screw structure adopts a low-shear conveying element and a small-angle meshing dispersion mixing block. The barrel temperature is 350-390℃, the screw speed is 200-400rpm, and the vacuum exhaust is -0.06 to -0.09Mpa.

[0010] As a further supplement to this technical solution, in step (2), the single screw parameters are L / D=30–35, the barrel temperature is 350–385℃, the screw speed is 10–25rpm, a spiral guide groove is set inside the die, the spiral angle is 10°-35°, the mandrel length is 30–60% of the flow channel length, and the flow channel cross-sectional area is gradually reduced.

[0011] As a further supplement to this technical solution, step (3) specifically involves: after the wire is extruded, it enters the traction system, and the tension is controlled at 0.1-0.3N; a floating wheel structure is adopted; and the tension is adjusted in real time with feedback.

[0012] As a further supplement to this technical solution, step (4) specifically means: the wire is immediately placed in a low-temperature air-cooling zone after extrusion, with a cooling rate ≥50℃ / min; final temperature ≤40℃; and cooling length ≥2m.

[0013] Its beneficial effects are as follows: the present invention achieves systematic optimization in the control of material microstructure through techniques such as fiber length maintenance control, perturbation rectification flow field design, low tension traction, and rapid quenching structure locking, thereby obtaining the following beneficial effects: significantly reducing the mechanical anisotropy of printed parts; significantly improving mechanical properties in the Z-axis direction; effectively improving fiber reinforcement efficiency; suppressing the secondary orientation effect during processing; and achieving fiber structure locking through rapid quenching. In summary, this invention, starting from the control of fiber spatial structure, achieves a significant reduction in the anisotropy of mechanical properties of short fiber reinforced PEEK materials in 3D printing applications through multi-stage synergistic control, while also taking into account the requirements of high strength, high stability, and industrial production. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a traditional straight-through flow channel (undisturbed structure) and a flow channel using spiral guide grooves (disturbed structure); Note: Orange arrows indicate the direction of melt flow, blue arrows indicate the direction of local circulation / disturbance, and short fibers are represented by short black lines; Figure 2 This is a schematic diagram of the structure of the fiber height orientation in the traditional straight flow channel and the random orientation of the fiber in the perturbation flow channel of the present invention. Detailed Implementation

[0015] To facilitate a clearer understanding of this technical solution for those skilled in the art, the following will be described in conjunction with the appendix. Figure 1-2 The technical solution of the present invention is described in detail below: A low anisotropy short fiber reinforced PEEK 3D printing filament comprises the following components by weight percentage: PEEK resin: 75–90 wt%; short fiber reinforcement: 10–25 wt%; interface compatibilizer PEI or coupling agent KH550: 0–3 wt%; antioxidant or heat stabilizer: 0–1 wt%.

[0016] PEEK is a semi-crystalline polyether ether ketone with a melting point of 330–350℃.

[0017] The short fiber reinforcement consists of short carbon fibers or short glass fibers.

[0018] The initial length of the short fiber reinforcement is 0.2–1.0 mm, preferably 0.3–0.8 mm, to ensure a balance between reinforcement efficiency and processability. Furthermore, the aspect ratio of the short fiber reinforcement is 10–100.

[0019] A method for preparing low anisotropy short fiber reinforced PEEK 3D printing filament includes the following steps: Step (1) PEEK fiber dispersion granulation: A parallel co-rotating twin-screw extruder with parameters L / D=40-52 and screw diameter: 25-50mm is used. It has a zoned temperature control system. PEEK resin is added through the main hopper, and short fibers are added in the rear section of the melting zone through the side feed port. The screw structure adopts low-shear conveying elements and small-angle meshing dispersion and mixing blocks. The barrel temperature is 350-390℃, the screw speed is 200-400rpm, and the vacuum exhaust is -0.06 to -0.09Mpa. Control indicators: the average fiber length in the outlet granules is ≥60% of the original length; the length distribution is uniform; there is no obvious fiber agglomeration. The fiber length is counted by microsection.

[0020] Step (2) Reinforced PEEK filament extrusion; single screw parameters are L / D=30–35, barrel temperature: 350–385℃, screw speed: 10–25rpm, a spiral guide groove is set inside the die, the spiral angle is 10°-35°, the mandrel length is 30–60% of the flow channel length, and the flow channel cross-sectional area is gradually reduced; when the melt passes through this disturbance structure: the original unidirectional shear flow field is broken; the melt forms an alternating rotating flow; the fiber undergoes a micro-angle deflection; the orientation factor decreases. This structure does not change the total flow rate, but only changes the local flow field structure.

[0021] Step (3): Low-tension floating traction system; after the wire is extruded, it enters the traction system and the tension is controlled at 0.1-0.3N; a floating wheel structure is adopted; real-time tension feedback adjustment is used; axial stretching of the wire, secondary fiber orientation, and accumulation of internal residual stress are avoided.

[0022] Step (4) Rapid quenching and shaping: The wire is immediately placed in the low-temperature air-cooling zone after extrusion, with a cooling rate of ≥50℃ / min; final temperature ≤40℃; cooling length ≥2m. The purpose of rapid quenching is to lock the spatial distribution after fiber disturbance; suppress crystallization-induced orientation enhancement; reduce crystal preferred orientation; unlike slow crystallization control, this invention emphasizes: structural locking, rather than crystallization optimization.

[0023] In the above embodiments, a built-in spiral disturbance mandrel structure is used to regulate the melt flow field.

[0024] In other embodiments of the present invention, a static mixing unit structure can be used instead; the static mixing unit structure sets several levels of static mixing units (such as staggered flow dividers) in the die flow channel: it can cause the melt to split and recombine; change the local flow velocity distribution; break the unidirectional shear field; this structure can also achieve: fiber orientation disturbance; reduce the orientation factor.

[0025] The performance of the present invention is further verified through the following examples: Example 1 Preparation of 25% short carbon fiber reinforced PEEK wire (PEEK 75% / short carbon fiber 25%): The wire was drawn into wire according to the above granulation and extrusion process, and the wire diameter was finally controlled at 1.75mm±0.05mm. The wire was printed in a high temperature FDM device with a nozzle temperature of 410℃ and a chamber temperature of 150℃.

[0026] Example 2: Preparation of 15% short carbon fiber reinforced PEEK wire (85% PEEK / 15% short carbon fiber). The wire was drawn into wire according to the above granulation and extrusion process, and the wire diameter was finally controlled at 1.75mm ± 0.05mm. The wire was printed in a high-temperature FDM device with a nozzle temperature of 410℃ and a chamber temperature of 150℃. The specific properties are shown in Table 1. Table 1 Comparative Example 1: Based on Example 1, all other processes are the same, except that a common straight-through mold is used.

[0027] Comparative Example 2: Based on Example 2, all other processes are the same, except that high traction tension is used.

[0028] The specific performance data for Comparative Example 1 and Comparative Example 2 are shown in Table 2: Table 2 The above technical solutions only embody the preferred technical solutions of the present invention. Any modifications that may be made by those skilled in the art to certain parts thereof embody the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A low-anisotropy short-fiber reinforced PEEK 3D printing filament, characterized in that, The product comprises the following components by weight percentage: PEEK resin: 75–90 wt%; short fiber reinforcement: 10–25 wt%; interface compatibilizer PEI or coupling agent KH550: 0–3 wt%; antioxidant or heat stabilizer: 0–1 wt%.

2. The low anisotropy short fiber reinforced PEEK 3D printing filament according to claim 1, characterized in that, The PEEK is a semi-crystalline polyether ether ketone with a melting point of 330–350°C.

3. The low anisotropy short fiber reinforced PEEK 3D printing filament according to claim 1, characterized in that, The short fiber reinforcement is short carbon fiber or short glass fiber.

4. The low anisotropy short fiber reinforced PEEK 3D printing filament according to claim 3, characterized in that, The initial length of the short fiber reinforcement is 0.2–1.0 mm.

5. The low anisotropy short fiber reinforced PEEK 3D printing filament according to claim 1, characterized in that, The aspect ratio of the short fiber reinforcement is 10–100.

6. A method for preparing a low-anisotropy short-fiber reinforced PEEK 3D printing filament according to any one of claims 1-5, characterized in that, Includes the following steps: Step (1): PEEK fiber-reinforced dispersion and granulation; Step (2), reinforced PEEK wire extrusion; Step (3), low-tension floating traction system; Step (4): Rapid quenching and shaping.

7. The method for preparing a low anisotropy short fiber reinforced PEEK 3D printing filament according to claim 6, characterized in that, Step (1) uses a parallel co-rotating twin-screw extruder with parameters L / D=40-52, screw diameter: 25-50mm, and a zoned temperature control system. PEEK resin is added through the main hopper, and short fibers are added through the side feed port in the rear section of the melting zone. The screw structure adopts low-shear conveying elements and small-angle meshing dispersion mixing blocks. The barrel temperature is 350-390℃, the screw speed is 200-400rpm, and the vacuum exhaust is -0.06 to -0.09Mpa.

8. The method for preparing a low anisotropy short fiber reinforced PEEK 3D printing filament according to claim 6, characterized in that, In step (2), the single screw parameters are L / D=30–35, barrel temperature: 350–385℃, screw speed: 10–25rpm, a spiral guide groove is set inside the die, the spiral angle is 10°-35°, the mandrel length is 30–60% of the flow channel length, and the flow channel cross-sectional area is gradually reduced.

9. The method for preparing a low anisotropy short fiber reinforced PEEK 3D printing filament according to claim 6, characterized in that, The specific steps (3) are as follows: after the wire is extruded, it enters the traction system and the tension is controlled at 0.1-0.3N; a floating wheel structure is adopted; and the tension is adjusted in real time with feedback.

10. The method for preparing a low anisotropy short fiber reinforced PEEK 3D printing filament according to claim 6, characterized in that, The specific steps (4) are as follows: the wire is immediately placed in the low-temperature air cooling zone after extrusion, with a cooling rate of ≥50℃ / min; final temperature ≤40℃; and cooling length ≥2m.

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