Continuous fiber reinforced 3D (three-dimensional) printing foaming part as well as preparation method and application thereof

Abstract

The invention discloses a continuous fiber reinforced 3D printing foaming part and a preparation method and application thereof, and relates to the technical field of 3D printing. According to the preparation method of the continuous fiber reinforced 3D printing foaming part, provided by the invention, the coaxial continuous fiber which is pretreated and has specific diameter and strength is introduced into the polymer foaming melt while the polymer foaming melt is extruded, so that the compatibility between the obtained continuous fiber and the polymer foaming melt is excellent; according to the present invention, the polymer foaming melt is added, such that the foaming skin layer formed by the polymer foaming melt can synchronously provide the supporting effect along with the fiber when the product is pulled by the external force, the mechanical property of the product is improved, the tensile breaking strength of the obtained product can achieve more than 400 MPa, the density is not higher than 0.95 g / cm < 3 >, the strength requirement on the continuous fiber is reduced, and the production cost is reduced. Therefore, the size error below 3% can be obtained, and the precision is excellent.

Description

Technical Field

[0001] The present invention relates to the field of 3D printing technology, and in particular, to a continuous fiber reinforced 3D printed foamed part, a preparation method thereof and an application thereof. Background Art

[0002] 3D printing technology can realize free printing of structures according to designs without molds, and thus has currently become an important development direction in the field of polymer material processing. However, the existing 3D printed parts usually have a solid structure and are relatively heavy in texture. With the increasing requirements for lightweight parts in fields such as aerospace and sports equipment, how to reduce the density of 3D printed parts has currently become a focus.

[0003] Foaming existing 3D printed parts or controllably stacking foamed melts to form 3D printed parts can form foamed 3D parts, which is an important means to reduce the weight of 3D printed parts. However, the existing foamed 3D parts have disadvantages such as low precision, poor stability and low strength, which limit their applications.

[0004] In order to improve the strength of existing foamed 3D parts, the prior art Yang, C., Tian, X., Liu, T.,Cao, Y. and Li, D.3D printing for continuous fiber reinforced thermoplasticcomposites: mechanism and performance, Rapid Prototyping Journal, Vol. 23 No.1, pp. 209-215(2017). proposed that continuous carbon fibers can be introduced as a reinforcing phase into the foamed filament melt. However, when introducing carbon fibers during the controllable stacking process of the foamed melt, there is a problem of difficulty in taking into account both the precision and strength of the foamed 3D part: due to the high strength and high hardness of carbon fibers themselves, the foamed melt containing carbon fibers is prone to dimensional deformation during the stacking of small lattice units, resulting in a decrease in the printing precision of the part. However, introducing fibers with low strength has limited improvement in the strength performance of 3D printed parts. At the same time, the currently commonly used preparation methods for introducing continuous fibers into the foamed filament melt usually have problems of insufficient compatibility between the foamed melt and the continuous fibers, which easily leads to delamination between the skin layer formed by the foamed melt and the continuous fiber core after forming the part, further resulting in a decrease in the strength of the 3D printed part. Therefore, there is an urgent need to provide a preparation method for foamed 3D parts that can improve the strength of the part and ensure its precision at the same time. Summary of the Invention

[0005] To solve the deficiencies of the prior art, the present invention provides a method for preparing a continuously fiber-reinforced 3D printed foamed part, in which coaxial continuous fibers with a specific diameter and after pretreatment are introduced before extruding the polymer foamed melt, improving the bonding force between the polymer and the fibers. While the part has excellent strength, it is not necessary to use reinforcing fibers with too high hardness, so excellent precision can also be obtained.

[0006] Another object of the present invention is to provide a continuously fiber-reinforced 3D printed foamed part.

[0007] Another object of the present invention is to provide an application of a continuously fiber-reinforced 3D printed foamed part.

[0008] The above objects of the present invention are achieved by the following technical solutions: A method for preparing a continuously fiber-reinforced 3D printed foamed part, comprising the following steps: S1. Immerse the continuous fiber in a pretreatment liquid at a temperature of 30 - 50 °C, and dry it after immersion to obtain pretreated continuous fiber; the strength of the continuous fiber is 1 - 8 cN / dtex, and the diameter is 0.1 - 0.9 mm; the pretreatment liquid includes at least one solute of maleic anhydride, polydopamine, tetrahydrofuran, and acetone; S2. Melt the polymer particles containing a blowing agent, add the pretreated continuous fiber obtained in step S1 for coaxial co-extrusion to obtain a foamed filament melt, and the diameter of the foamed filament melt is 0.2 - 1.2 mm; the foamed filament melt includes a core and a foamed cortex wrapped on the surface of the core, and the core is a continuous fiber; S3. 3D print the foamed filament melt obtained in step S1 along a planned path to obtain a continuously fiber-reinforced 3D printed foamed part.

[0009] In the preparation method provided by the present invention, in step S1, the continuous fiber is pretreated to form a film on the surface of the continuous fiber, and then in step S2, the continuous fiber with a specific diameter is co-axially co-extruded with the polymer raw material particles, and at the same time, the diameter of the foamed melt itself is controlled to adjust the "ratio" between the continuous fiber and the polymer foamed filament melt. Through pretreatment and diameter control, the present invention can improve the bonding force between the polymer foamed melt raw material and the continuous fiber. After melt foaming, it can avoid the separation between the continuous fiber core and the foamed cortex. The obtained part not only has the characteristics of light weight, but also can improve strength and precision by the action of the continuous fiber.

[0010] The commonly selected reinforcing fibers in this field include glass fibers, carbon fibers, aramid fibers, etc. The strength is generally in the range above 15 cN / dtex (for example, for the commonly used reinforcing fiber, carbon fiber, its strength is generally 18 cN / dtex). Although it can significantly improve the strength of the workpiece, during the process of manufacturing 3D printing foamed workpieces, these high-strength fibers are prone to dimensional deformation when stacked in small lattice units, resulting in a decrease in the printing accuracy of the workpiece. At the same time, the principle by which the above-mentioned reinforcing fibers enhance the workpiece is similar to the "reinforced concrete" system: when the workpiece is bent or pulled by an external force, the continuous fibers act as "reinforcing bars" to provide support. Even if the foamed skin outside the continuous fibers breaks, due to the high strength of the continuous fibers themselves, they can still remain unbroken.

[0011] Although the continuous fibers with a strength of 1 - 8 cN / dtex selected in the present invention are not as strong as the conventional reinforcing fibers themselves, the preparation method provided by the present invention improves the compatibility and bonding force between the continuous fibers and the foamed skin, enabling the skin to provide support synchronously with the fibers when the workpiece is pulled by an external force. Therefore, even if the present invention selects continuous fibers with a lower strength, it can still achieve an improvement in the strength of the workpiece. At the same time, since the strength of the continuous fibers in the present invention is not high, the fibers are not easily deformed during the controllable stacking of 3D printing in the process of stacking small lattice units. Therefore, the workpieces obtained by the present invention also have higher dimensional accuracy.

[0012] The composition and temperature of the treatment liquid during pretreatment in step S1 will affect the compatibility between the continuous fibers and the foamed melt. The inventors of the present application have found through a large number of experimental studies that among many reagents with functions such as improving compatibility and acting as adhesives, only maleic anhydride, polydopamine, tetrahydrofuran, and acetone have good compatibility with both the continuous fibers and the foamed melt in the present invention. Pretreating and modifying the fibers with at least one of the above four reagents can improve the bonding between the continuous fibers and the foamed melt, enabling the continuous fibers to fully exert their reinforcing effect. And when the temperature of the pretreatment liquid is 30 - 50 °C, the compatibility between the continuous fibers and the foamed melt can be further improved. It is speculated that because the temperature is appropriate, the film formed by the pretreatment liquid on the surface of the continuous fibers has higher uniformity. In the specific embodiment of the present invention, the solvent in the pretreatment liquid includes water.

[0013] The melt diameter of the foamed filament and the diameter of the continuous fiber itself will also affect the interaction between the foamed skin layer and the continuous fiber core. Controlling the above two diameters is equivalent to controlling the ratio between the continuous fiber and the foamed skin layer. If the proportion of the continuous fiber is too high or too low, the resulting parts cannot achieve both high strength and high precision: when the diameter of the continuous fiber is too low, the improvement of the part strength is not obvious; when the diameter of the continuous fiber is too high, the specific surface area of the fiber decreases, the contact surface with the foamed melt decreases, and the interaction force between the two decreases, which will also lead to a decrease in the part strength.

[0014] In a specific embodiment of the present invention, the method for preparing a continuous fiber reinforced 3D printed foamed part provided by the present invention is carried out in a 3D printing device including the following functional units: a feeding unit, an extrusion unit, a printer moving bracket, a stacking platform, and a printer housing.

[0015] In a specific embodiment of the present invention, the co-extrusion by adding continuous fibers in step S2 is achieved by introducing the continuous fiber feeding port through an opening at the side end of the extrusion die of the extrusion unit.

[0016] In a specific embodiment of the present invention, the melt diameter of the foamed filament can be controlled to be 0.2 - 1.2 mm by making the size of the extrusion die of the single-screw extruder be 0.01 - 1.0 mm.

[0017] In a specific embodiment of the present invention, the coaxial co-extrusion described in step S2 means that the melt formed by the pretreated continuous fiber and the molten polymer particles shares the same axis. During the extrusion process of the present invention, the molten polymer particles will coat the outside of the pretreated continuous fiber. The shapes of the melt formed by the continuous fiber and the molten polymer particles are approximately a cylinder and a hollow cylinder respectively. The line connecting the centers of the two ends of the cylinder or the hollow cylinder is the axis of the cylinder or the hollow cylinder. In the foamed filament melt prepared by the coaxial co-extrusion method described in step S2, the continuous fiber core and the foamed skin layer are coaxial, where the foamed skin layer is prepared by foaming the molten polymer particles and can also be approximated as a hollow cylinder.

[0018] Preferably, the impregnation time in step S1 is 30 - 300 s.

[0019] Preferably, the continuous fiber in step S1 includes PET (polyethylene terephthalate) fiber.

[0020] Using PET continuous fiber to construct the core of the foamed filament melt can obtain 3D printed foamed parts with both higher strength and precision.

[0021] Preferably, the diameter of the continuous fiber in step S1 is 0.1 - 0.3 mm.

[0022] More preferably, the fineness of the continuous fiber described in step S1 is 150 to 300 D.

[0023] Preferably, the melting and the coaxial co-extrusion described in step S2 are carried out by a single-screw extruder, and the single-screw extruder includes a first heating section, a second heating section, and a third heating section. The temperature of the first heating section is 0 to 30 °C, the temperature of the second heating section is 150 to 300 °C, and the temperature of the third heating section is 200 to 390 °C. The real-time temperature of the third heating section is higher than that of the second heating section.

[0024] By using the above extrusion process for extrusion, controllable foaming of the polymer raw material can be achieved, thereby further enhancing the bonding force between the continuous fiber and the foamed skin layer. Specifically, after the polymer particles containing the foaming agent are conveyed into the screw structure of the first heating section, the particle temperature is relatively low, which can reduce the loss of the foaming agent and realize the stable conveying of the material. The particles containing the foaming agent truly start to melt in the screw of the second heating section and are compacted by the screw structure, realizing the densification between the particle structures and further preventing the escape of the foaming agent; the particles containing the foaming agent continue to melt and foam in the third section of the screw, and the stable conveying of the foamed melt to the die of the extruder is realized through the metering property of the screw structure, and controllable foaming can be achieved at the moment of extrusion. The foamed skin layer formed by controllable foaming has a uniform surface, so it can fully contact and be compatible with the continuous fiber. There is a larger contact area and fewer air gaps between the two, enabling good interfacial bonding performance between the skin layer and the inner core. Therefore, the parts obtained by the present invention can make full use of the reinforcing performance of the fiber inner core and thus have more excellent strength. At the same time, due to controllable foaming, the present invention can further reduce the density while ensuring the strength of the parts, realizing more functionalization.

[0025] In a specific embodiment of the present invention, the temperature of the first heating section described in step S2 is controlled to be 0 to 30 °C by connecting a temperature control component, and the temperature control component includes at least one of a cold air system and a water cooling system. The polymer particles containing the foaming agent do not expand in the first screw structure.

[0026] In a specific embodiment of the present invention, the temperature control accuracy of the second heating section and the third heating section described in step S2 is 0.5 to 5 °C, preferably 1 to 3 °C.

[0027] In a specific embodiment of the present invention, the residence time of the polymer particles containing the foaming agent in the second heating section and the third heating section described in step S2 is 0.1 to 1.5 s, preferably 0.2 to 1.0 s, and more preferably 0.3 to 0.8 s.

[0028] Preferably, the diameter of the foamed filament melt described in step S2 is 0.3 to 0.5 mm.

[0029] When the diameter of the foamed wire melt in step S2 is 0.3-0.5 mm, the diameter of the continuous fiber in step S1 is 0.1-0.5 mm, and the diameter of the continuous fiber is less than the diameter of the foamed wire melt. The above adjustment can further improve the precision of the manufactured product.

[0030] More preferably, the thickness of the foamed skin layer in the foamed wire melt in step S2 is 0.08-0.3 mm.

[0031] Preferably, the speed of the coaxial co-extrusion in step S2 is 1-3 kg / h.

[0032] In a specific embodiment of the present invention, the screw speed of the single screw extruder in step S2 is 10-50 rpm.

[0033] Preferably, before melting the polymer particles containing the foaming agent in step S2, the step of low temperature treatment of the polymer particles containing the foaming agent is also included, and the low temperature treatment is carried out under the conditions of -40 to 0°C and 1 to 30% humidity. The time of low temperature treatment is not limited in the present invention, as long as the temperature of the raw material particles is basically consistent with the ambient temperature. Low temperature treatment can help avoid the loss of the foaming agent.

[0034] Preferably, the content of the blowing agent in the polymer particles containing the blowing agent in step S2 is 0.1-10 wt %, more preferably 0.5-8 wt %.

[0035] In a specific embodiment of the present invention, the shape of the polymer particles containing a foaming agent in step S2 includes at least one of a circular, an elliptical, and a wedge-shaped shape, an average diameter of 0.5 to 5.0 mm, a fluctuation range of the average diameter of 0.5 to 1 mm, and a hardness of Shore A10 to Shore D85.

[0036] Preferably, the polymer particles containing a foaming agent in step S2 include the following preparation raw materials calculated by mass: 80-100 parts of polymer, 0.5-10 parts of foaming agent, 0-10 parts of nucleating agent, 0-0.5 parts of antioxidant.

[0037] Preferably, the polymer includes at least one of an amorphous polymer, a semi-crystalline polymer, a crystalline polymer, and a thermoplastic elastomer.

[0038] More preferably, the polymer has a melting point of 70-400° C. and a hardness of 30A-85D.

[0039] More preferably, the amorphous polymer comprises at least one of polystyrene (PS), polymethyl methacrylate (PMMA), polyetherimide (PEI), polyimide (PI), and polysulfone (PSF).

[0040] More preferably, the semi-crystalline polymer comprises at least one of polyethylene terephthalate (PET), polylactic acid (PLA), and polyetheretherketone (PEEK).

[0041] More preferably, the crystalline polymer comprises at least one of polyethylene (PE), polypropylene (PP), and nylon (PA).

[0042] More preferably, the thermoplastic elastomer comprises at least one of polyurethane (PU), thermoplastic polyester elastomer (TPEE), and polyamide elastomer (PEBA).

[0043] Preferably, the antioxidant comprises at least one of amine antioxidants, phosphorus antioxidants, and mercaptan antioxidants.

[0044] Preferably, the nucleating agent comprises at least one of calcium carbonate, talcum powder, mica, montmorillonite, nano-silica, carbon black, and carbon nanotubes.

[0045] Preferably, the foaming agent comprises at least one of fluid foaming agents and solid foaming agents.

[0046] In a specific embodiment of the present invention, the polymer particles containing the foaming agent in step S2 are prepared by blending the polymer particles with the foaming agent. Among them, when the foaming agent is a fluid foaming agent, the polymer particles are blended with the foaming agent by impregnation; when the foaming agent is a solid foaming agent, at least one of PE (polyethylene) and EVA (ethylene-vinyl acetate copolymer) is used as a foaming agent masterbatch to be mixed with the solid foaming agent, and then blended with the polymer particles. The purpose of adding the foaming agent masterbatch is to increase the particle size of the solid foaming agent. The particle size of the solid foaming agent is usually small, which is not conducive to foaming.

[0047] More preferably, the fluid foaming agent comprises supercritical fluids.

[0048] More preferably, the supercritical fluid comprises at least one of CO2, N2, alkanes, and hydrochlorofluorocarbon blowing agents (HCFC).

[0049] More preferably, the solid foaming agent comprises at least one of expandable microspheres, carbonates, N,N'-dinitrosopentamethylenetetramine, and azodicarbonamide.

[0050] More preferably, the particle size of the nucleating agent is 0.05~5 μm.

[0051] Preferably, the printing temperature of the 3D printing in step S3 is 30~150°C, preferably 40~90°C, and the temperature control accuracy is 1~5°C, preferably 1~3°C.

[0052] In a specific embodiment of the present invention, the printing temperature of the 3D printing in step S3 is the temperature of the single-screw extruder die at the extrusion port in step S1, that is, the extrusion temperature.

[0053] Preferably, the rotation angle of the 3D printing in step S3 is 0~80°, preferably 0~70°, and the rotational angular velocity is 0~5 rad / s, preferably 0~3 rad / s.

[0054] In a specific embodiment of the present invention, the stacking linear velocity of the 3D printing in step S3 is 80~120 mm / s.

[0055] The present invention also protects a continuous fiber-reinforced 3D printed foamed part prepared by the above preparation method.

[0056] The present invention also protects the application of the above continuous fiber-reinforced 3D printed foamed part in the fields of shoe materials, medical consumables, and handicrafts.

[0057] Compared with the prior art, the present invention has the following beneficial effects: When preparing a continuous fiber-reinforced 3D printed foamed part by using the preparation method provided by the present invention, it not only has good foaming performance, and the density is not higher than 0.95 g / cm 3 , at the same time, the tensile fracture strength can reach more than 400 MPa, which is 172% of the part without introducing continuous fibers for reinforcement, and the part provided by the present invention has a dimensional error of less than 3%, indicating that the method of the present invention can also take into account the accuracy of the part. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a schematic diagram of a 3D printing device for introducing a fiber feeding port at the side end opening of the extrusion die in the present invention. Among them, the reference numerals are as follows: 1, raw material bin; 2, metering screw; 3, air-cooled temperature control system; 4, conveying hose; 5, temperature control system; 6, heating jacket; 7, micro extrusion die; 8, continuous fiber feeding gear; 9, moving bracket; 10, fiber filament roll; 11, stacking platform; 12, printer housing.

[0059] Figure 2 It is a detailed schematic diagram of the extrusion die of the 3D printing device in the present invention. Among them, the reference numerals are as follows: 13, polymer melt containing blowing agent; 14, micro extrusion die; 15, continuous fiber; 16, continuous fiber-reinforced polymer foamed melt. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0060] The present invention will be further described below in conjunction with specific embodiments. However, the embodiments do not impose any form of limitation on the present invention. Unless otherwise specified, the raw material reagents used in the embodiments of the present invention are conventionally purchased raw material reagents. Among them, the raw material information used in each embodiment and comparative example is as follows (the part related to hardness refers to Shore hardness): Amorphous polymer A: Polystyrene PS, grade GPPS158K, Yangzi BASF.

[0061] Semicrystalline polymer B: Polyetheretherketone PEEK, grade 1000, Mitsubishi Chemical.

[0062] Thermoplastic elastomer C: Thermoplastic polyurethane TPU, hardness 60A, BASF Germany.

[0063] Blowing agent: Expandable microspheres, commercially available.

[0064] Nucleating agent: Polystyrene, average particle size of 2 μm, commercially available.

[0065] Antioxidant: Mercaptan antioxidant, commercially available.

[0066] Continuous fiber: PET fiber, commercially available, strength of 4 cN / dtex, fineness of 200 D.

[0067] Aramid fiber, commercially available, strength of 20 cN / dtex, fineness of 200 D.

[0068] Cellulose fiber, commercially available, strength of 10 cN / dtex, fineness of 250 D.

[0069] Carbon fiber, commercially available, strength of 18 cN / dtex, fineness of 150 D.

[0070] PTFE (polytetrafluoroethylene) fiber, commercially available, strength of 5.8 cN / dtex, fineness of 180 D.

[0071] Chopped fiber: PET fiber, commercially available, diameter of 0.2 mm.

[0072] Examples 1 to 12 This example provides a preparation method for continuously fiber-reinforced 3D printing foamed parts with a series of different processing parameters and raw materials, including the following steps: S1. Immerse the continuous fiber in a pretreatment solution at a temperature of 40 °C. After immersion for 2 min, dry it to obtain pretreated continuous fiber; the continuous fiber is PET fiber with a diameter of 0.1 - 0.9 mm; the pretreatment solution contains 50 wt% polydopamine, and the solvent is water; S2. Under the conditions of -20 °C and 1% humidity, perform low-temperature treatment on the polymer particles containing a foaming agent until the particle temperature reaches -20 °C. Feed the particles into the extrusion unit of a 3D printing device to melt the polymer particles containing the foaming agent, and add the pretreated continuous fiber obtained in step S1 for coaxial coextrusion to obtain a foamed filament melt. The foamed filament melt contains a continuous fiber core and a foamed skin layer wrapped on the surface of the core, with a diameter of 0.2 - 1.2 mm; the melting and the coaxial coextrusion are carried out using a single-screw extruder. The single-screw extruder includes a second heating section and a third heating section. The temperature of the first heating section is 0 - 30 °C, the temperature of the second heating section is 150 - 300 °C, the temperature of the third heating section is 200 - 390 °C, and the real-time temperature of the third heating section is higher than that of the second heating section; the first heating section is connected to a cold air system to control the temperature, and the screw rotation speed of the single-screw extruder is 25 rpm; S3. Perform 3D printing on the foamed filament melt obtained in step S1 according to the planned path to obtain a continuous fiber-reinforced 3D printed foamed part; The above preparation method is carried out in a 3D printing device whose extrusion unit includes a single-screw extruder. The 3D printing device includes the following functional units: a feeding unit, an extrusion unit, a printer moving bracket, a stacking platform, and a printer housing; the side end opening of the extrusion die of the single-screw extruder introduces a continuous fiber wire feeding port, as Figures 1-2 shown. According to Figure 2 , the polymer melt 13 containing a foaming agent will successively experience a cell nucleation stage and a cell growth stage during extrusion, and then a continuous fiber-reinforced polymer foamed melt is obtained after extrusion.

[0073] In this embodiment, by mass, it includes the following components: 100 parts of polymer, 5 parts of foaming agent, 5 parts of nucleating agent, and 0.3 parts of antioxidant.

[0074] The specific processing parameters and preparation raw materials in this embodiment are shown in Table 1 below: Table 1. Specific processing parameters in Examples 1 - 12 Example 13 A preparation method of a continuous fiber-reinforced 3D printed foamed part, which is only different from Example 5 in that: The coextrusion speed in step S2 is 0.8 kg / h.

[0075] Example 14 A preparation method of a continuously fiber-reinforced 3D printed foamed part, which is only different from Example 5 in that: The co-extrusion speed described in step S2 is 3.2 kg / h.

[0076] Example 15 A preparation method of a continuously fiber-reinforced 3D printed foamed part, which is only different from Example 5 in that: The temperature of the first heating section described in step S2 is 100°C.

[0077] Example 16 A preparation method of a continuously fiber-reinforced 3D printed foamed part, which is only different from Example 5 in that: The continuous fiber described in step S1 is a PTFE fiber.

[0078] Comparative Example 1 A preparation method of a 3D printed foamed part, which is only different from Example 5 in that: No continuous fiber is introduced in step S2, that is, no side opening is made at the extrusion die of the single-screw extruder in the 3D printing device.

[0079] Comparative Example 2 A preparation method of a continuously fiber-reinforced 3D printed foamed part, which is only different from Example 5 in that: The diameter of the continuous fiber in step S1 is 0.08 mm, and the diameter of the foamed filament melt in step S2 is 0.38 mm.

[0080] Comparative Example 3 A preparation method of a continuously fiber-reinforced 3D printed foamed part, which is only different from Example 5 in that: The diameter of the continuous fiber described in step S1 is 1.1 mm, and the diameter of the foamed filament melt in step S2 is 1.2 mm.

[0081] Comparative Example 4 A preparation method of a short fiber-reinforced 3D printed foamed part, which is only different from Example 5 in that: In step S2, the polymer particles containing a foaming agent are blended with short-cut fibers and then melt-extruded; no continuous fiber is introduced during extrusion, that is, no side opening is made at the extrusion die of the single-screw extruder in the 3D printing device.

[0082] Comparative Example 5 A preparation method of a continuously fiber-reinforced 3D printed foamed part, which is only different from Example 5 in that: The continuous fiber described in step S1 is a carbon fiber.

[0083] Comparative Example 6 A preparation method of a continuous fiber reinforced 3D printed foamed part, the difference from Example 5 is only that: The continuous fiber described in step S1 is aramid fiber.

[0084] Comparative Example 7 A preparation method of a continuous fiber reinforced 3D printed foamed part, the difference from Example 5 is only that: The continuous fiber described in step S1 is cellulose fiber.

[0085] Comparative Example 8 A preparation method of a continuous fiber reinforced 3D printed foamed part, the difference from Example 5 is only that: No pretreatment is carried out in step S1.

[0086] Comparative Example 9 A preparation method of a continuous fiber reinforced 3D printed foamed part, the difference from Example 5 is only that: The pretreatment solute in step S1 is maleic anhydride grafted polypropylene.

[0087] Comparative Example 10 A preparation method of a continuous fiber reinforced 3D printed foamed part, the difference from Example 5 is only that: The pretreatment temperature in step S1 is 10°C.

[0088] Performance Test Specimen preparation: 3D print a specimen with a size of 30×30×1.2 mm, a filling pattern of "X" type, and a filling density of 30%.

[0089] Tensile fracture strength test: Measure through a tensile testing machine.

[0090] Dimensional error measurement: Measure through a caliper.

[0091] Density test: Test through a densitometer.

[0092] Processing behavior measurement: Measure by visual observation.

[0093] Appearance morphology measurement of the part: Measure by visual observation.

[0094] The specific test data are shown in Table 2 below: Table 2. Performance test data of 3D printed foamed parts obtained from examples and comparative examples As can be seen from the data in Table 2 above, when preparing a continuously fiber-reinforced 3D printed foamed part by using the preparation method provided by the present invention, the tensile fracture strength of the obtained part can reach more than 400 MPa, which is 172% of the part without introducing continuous fibers for reinforcement (Comparative Example 1), indicating that the method of the present invention can greatly improve the strength of the 3D foamed part. At the same time, the part provided by the present invention has a dimensional error of less than 3%, indicating that the method of the present invention can also take into account the precision of the part. In addition, the part of the present invention also has a density of not higher than 0.95 g / cm 3 and excellent foaming performance.

[0095] According to Examples 5 to 10, the diameter of the foamed filament melt in step S2 is higher (Examples 7, 9 to 10), and the comprehensive performance of the obtained part decreases. Therefore, the present invention preferably selects the diameter of the foamed filament melt in step S2 to be 0.3 to 0.5 mm. According to Example 11, too high a thickness of the foamed skin layer will also lead to a decrease in performance. Therefore, the present invention preferably selects the thickness of the foamed skin layer in the foamed filament melt to be 0.08 to 0.3 mm. According to Examples 7 and 12, when the diameter of the foamed filament melt remains unchanged, the diameter of the continuous fiber increases (Example 12), and the density of the obtained part increases and the strength decreases. Therefore, the present invention preferably selects the diameter of the continuous fiber to be 0.1 to 0.3 mm.

[0096] According to Examples 5, 13 to 14, a higher co-extrusion speed will lead to a decrease in dimensional accuracy (Example 14), while a lower co-extrusion speed will result in a decrease in the strength and an increase in the density of the obtained part (Example 13). According to Example 15, using a conventional extrusion process (the temperature of the first heating section is as high as above 100°C) will affect the strength and precision performance of the part. As can be seen from Examples 5 and 16, when the preparation method provided by the present invention uses PET fiber as the inner core of the foamed filament melt, the performance of the obtained part is better, presumably because there is better compatibility between the PET fiber and the foamed filament melt.

[0097] According to Comparative Examples 1 and 4, without introducing continuous fibers (Comparative Example 1) or introducing short-cut fibers (Comparative Example 2), the performance of the obtained part is poor. Among them, introducing short-cut fibers as the reinforcing material does not significantly improve the strength of the part, and at the same time will lead to a decrease in dimensional accuracy, and instead results in a downward trend in the strength of the part.

[0098] According to Comparative Examples 2 to 3, too high or too low a diameter of the continuous fiber will lead to a decline in the performance of the obtained workpiece. Among them, when the diameter of the continuous fiber is too small (Comparative Example 2), the reinforcement effect is not obvious, and at the same time, it is easy to cause unstable wire feeding, which in turn affects the uniformity of the foamed filament melt during co-extrusion, resulting in large dimensional deviations and many defects in the workpiece, and further reducing the tensile fracture strength; when the diameter of the continuous fiber is too large (Comparative Example 3), the skin layer is relatively thin, and the continuous fiber is easily affected by the high temperature at the extrusion outlet during the extrusion process, resulting in fiber melting and deformation (manifested as melting and deformation of the foamed filament melt), and it cannot be extruded normally. At the same time, the high rigidity of the fiber leads to poor interfacial adhesion, low forming accuracy, many defects between interfaces, and low strength.

[0099] Comparative Examples 5 to 7 illustrate that, referring to the prior art, introducing conventional high-strength aramid fibers, carbon fibers or cellulose fibers into the foamed melt for reinforcement will lead to a decline in accuracy, which in turn affects the improvement of strength by the fibers.

[0100] According to Comparative Examples 8 to 10, the pretreatment step and its conditions also have an important impact on the performance of the workpiece. Without pretreatment, or too low pretreatment temperature or inappropriate solute will lead to a decline in the compatibility between the continuous fiber and the foamed melt, which in turn affects the performance.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A preparation method for a continuously fiber-reinforced 3D printed foamed part, characterized in that It includes the following steps: S1. Immerse continuous fibers in a pretreatment solution at a temperature of 30 to 50 °C, and dry after immersion to obtain pretreated continuous fibers; the strength of the continuous fibers is 1 to 8 cN / dtex, and the diameter is 0.1 to 0.9 mm; the pretreatment solution includes at least one solute of maleic anhydride, polydopamine, tetrahydrofuran, and acetone; S2. Melt polymer particles containing a foaming agent, add the pretreated continuous fibers obtained in step S1 for coaxial co-extrusion to obtain a foamed filament melt, and the diameter of the foamed filament melt is 0.2 to 1.2 mm; the foamed filament melt includes a core and a foamed skin layer wrapped on the surface of the core, and the core is continuous fibers; S3. Perform 3D printing on the foamed filament melt obtained in step S1 according to a planned path to obtain a continuous fiber-reinforced 3D printed foamed part.

2. The preparation method of the continuous fiber reinforced 3D printed foamed part according to claim 1, characterized in that, The continuous fibers in step S1 include PET fibers.

3. The preparation method of the continuous fiber reinforced 3D printed foamed part according to claim 1, wherein, The melting and the coaxial co-extrusion in step S2 are carried out using a single-screw extruder. The single-screw extruder includes a first heating section, a second heating section, and a third heating section. The temperature of the first heating section is 0 to 30 °C, the temperature of the second heating section is 150 to 300 °C, and the temperature of the third heating section is 200 to 390 °C. The real-time temperature of the third heating section is higher than that of the second heating section.

4. The preparation method of the continuous fiber-reinforced 3D printing foam part according to claim 1, characterized in that, The diameter of the foamed filament melt in step S2 is 0.3 to 0.5 mm.

5. The preparation method of the continuous fiber-reinforced 3D printed foamed part according to claim 1, wherein, The coaxial co-extrusion speed in step S2 is 1 to 3 kg / h.

6. The preparation method of the continuous fiber reinforced 3D printed foamed part according to claim 1, wherein, The polymer particles containing a foaming agent in step S2 include the following preparation raw materials calculated by mass fraction: 80 to 100 parts of polymer, 0.5 to 10 parts of foaming agent, 0 to 10 parts of nucleating agent, and 0 to 0.5 parts of antioxidant.

7. The preparation method of the continuous fiber reinforced 3D printed foamed part according to claim 6, characterized in that, It includes at least one of the following (a) to (d): (a) The polymer includes at least one of amorphous polymer, semi-crystalline polymer, crystalline polymer, and thermoplastic elastomer; (b) The antioxidant includes at least one of amine antioxidants, phosphorus antioxidants, and mercaptan antioxidants; (c) The nucleating agent includes at least one of calcium carbonate, talc, mica, montmorillonite, nano-silica, carbon black, and carbon nanotubes; (d) The foaming agent includes at least one of fluid foaming agents and solid foaming agents.

8. The preparation method of the continuous fiber-reinforced 3D printed foamed part according to claim 7, characterized in that, It includes at least one of the following (e) to (k): (e) The amorphous polymer includes at least one of polystyrene, polymethyl methacrylate, polyetherimide, polyimide, and polysulfone; (f) The semi-crystalline polymer includes at least one of polyethylene terephthalate, polylactic acid, and polyether ether ketone; (g) The crystalline polymer includes at least one of polyethylene, polypropylene, and nylon; (h) The thermoplastic elastomer includes at least one of polyurethane, polyester elastomer, and nylon elastomer; (i) The fluid foaming agent includes supercritical fluid; (j) The solid foaming agent includes at least one of expandable microspheres, carbonates, N,N'-dinitrosopentamethylenetetramine, and azodicarbonamide; (k) The particle size of the nucleating agent is 0.05 to 5 μm.

9. A continuous fiber reinforced 3D printed foamed part prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the continuous fiber reinforced 3D printed foamed part according to claim 9 in the fields of shoe materials, medical consumables, and handicrafts.

Images