A continuous fiber reinforced 3D printed foamed part and its preparation method and application

Abstract

The present invention discloses a continuous fiber reinforced 3D printed foamed part and its preparation method and application, which relate to the field of 3D printing technology. The preparation method of the continuous fiber reinforced 3D printed foamed part provided by the present invention introduces a pre-treated coaxial continuous fiber with a specific diameter and strength into the polymer foam melt while extruding the polymer foam melt. The obtained continuous fiber has excellent compatibility with the polymer foam melt, so that when the part is pulled by an external force, the foamed skin formed by the polymer foam melt can provide support synchronously with the fiber, thereby improving the mechanical properties of the part. The obtained part can achieve a tensile breaking strength of more than 400MPa and a density of no more than 0.95g / cm 3 At the same time, the strength requirements for continuous fibers are reduced, so a dimensional error of less than 3% can be achieved, with excellent precision.

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 and a preparation method and application thereof. Background Art

[0002] 3D printing technology, which allows for the freehand printing of designed structures without the need for molds, has become a significant development in polymer material processing. However, existing 3D-printed parts are typically solid and heavy. With the growing demand for lightweight parts in aerospace, sports equipment, and other fields, reducing the density of 3D-printed parts has become a key focus.

[0003] Foaming existing 3D-printed parts or controllably stacking foamed melts to form 3D-printed parts can create foamed 3D parts, an important means of reducing the weight of 3D-printed parts. However, existing foamed 3D parts suffer from shortcomings such as low precision, poor stability, and low strength, which limit their application.

[0004] In order to improve the strength of existing foamed 3D parts, the existing technology Yang, C., Tian, X., Liu, T., Cao, Y. and Li, D. 3D printing for continuous fiber reinforced thermoplastic composites: mechanism and performance, Rapid Prototyping Journal, Vol. 23 No. 1, pp. 209-215 (2017) proposed that continuous carbon fibers can be introduced into the foamed filament melt as a reinforcement phase. However, the introduction of carbon fibers during the controlled stacking process of the foamed melt has the problem of difficulty in balancing the precision and strength of the foamed 3D parts: due to the high strength and hardness of carbon fibers themselves, the foamed melt containing carbon fibers is prone to dimensional deformation when small lattice units are stacked, resulting in a decrease in the printing accuracy of the part. However, the introduction of low-strength fibers has limited improvement in the strength performance of the 3D printed parts. At the same time, the currently used preparation methods that introduce continuous fibers into the foaming filament melt often suffer from insufficient compatibility between the foaming melt and the continuous fibers. This can easily lead to delamination between the skin layer formed by the foaming melt and the inner core of the continuous fibers after the part is formed, further reducing the strength of the 3D-printed part. Therefore, there is an urgent need to provide a method for preparing foamed 3D parts that can improve part strength while ensuring its precision. Summary of the Invention

[0005] In order to address the shortcomings of the existing technology, the present invention provides a method for preparing continuous fiber-reinforced 3D-printed foamed parts. Before extruding the polymer foam melt, coaxial continuous fibers with a specific diameter and that have been pretreated are introduced to improve the bonding force between the polymer and the fibers. This allows the parts to have excellent strength without the need for reinforcing fibers with excessively high hardness, thereby achieving excellent precision.

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

[0007] Another object of the present invention is to provide an application of continuous fiber reinforced 3D printed foam parts.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] A method for preparing a continuous fiber reinforced 3D printed foamed part comprises the following steps:

[0010] S1. Immersing a continuous fiber in a pretreatment solution at a temperature of 30-50°C and drying the pretreated continuous fiber to obtain a pretreated continuous fiber; the continuous fiber has a strength of 1-8 cN / dtex and a diameter of 0.1-0.9 mm; the pretreatment solution comprises at least one solute selected from maleic anhydride, polydopamine, tetrahydrofuran, and acetone;

[0011] S2. Melting the polymer particles containing the foaming agent, adding the pretreated continuous fiber obtained in step S1 and coaxially coextruding to obtain a foamed filament melt, wherein the diameter of the foamed filament melt is 0.2 to 1.2 mm; the foamed filament melt comprises an inner core and a foamed skin wrapped around the surface of the inner core, wherein the inner core is a continuous fiber;

[0012] S3. The foamed filament melt obtained in step S1 is 3D printed according to the planned path to obtain a continuous fiber reinforced 3D printed foamed part.

[0013] The preparation method provided by the present invention involves pre-treating the continuous fibers in step S1 to form a film on the continuous fiber surface. Then, in step S2, the continuous fibers of a specific diameter are coaxially coextruded with polymer raw material particles. The diameter of the foaming melt itself is controlled to adjust the ratio between the continuous fibers and the polymer foaming filament melt. Through pre-treatment and diameter control, the present invention improves the bonding strength between the polymer foaming melt and the continuous fibers, preventing separation between the continuous fiber core and the foamed skin after melt foaming. The resulting product is not only lightweight but also boasts improved strength and precision, thanks to the continuous fibers.

[0014] Reinforcing fibers commonly used in this field include glass fiber, carbon fiber, and aramid fiber, with strengths generally exceeding 15 cN / dtex (for example, the commonly used reinforcing fiber, carbon fiber, generally has a strength of 18 cN / dtex). While these fibers can significantly improve the strength of the part, these high-strength fibers are prone to dimensional deformation when stacked in small lattice units during the manufacturing process of 3D-printed foamed parts, resulting in reduced printing accuracy. At the same time, the principle by which these reinforcing fibers reinforce the part is similar to that of a "rebar-concrete" system: when the part is bent or pulled by external forces, the continuous fibers act as "rebar" to provide support. Even if the foamed outer layer of the continuous fibers breaks, the continuous fibers themselves possess high strength and thus remain intact.

[0015] While the continuous fibers used in this invention, with a strength of 1-8 cN / dtex, are not as strong as conventional reinforcing fibers, the preparation method provided by this invention improves the compatibility and bonding between the continuous fibers and the foamed cortex, enabling the cortex to provide support alongside the fibers when the part is subjected to external forces. Therefore, even with the use of lower-strength continuous fibers, the present invention can still achieve an improvement in part strength. Furthermore, because the continuous fibers themselves are relatively weak, they are less likely to deform during the stacking of small lattice units during controlled 3D printing. Therefore, the resulting parts of this invention also exhibit higher dimensional accuracy.

[0016] The composition and temperature of the treatment liquid during the pretreatment in step S1 will affect the compatibility between the continuous fiber and the foaming melt. The inventors of this application have found through a large number of experimental studies that among the many reagents that have functions such as improving compatibility and being able to act as adhesives, only maleic anhydride, polydopamine, tetrahydrofuran, and acetone have good compatibility with the continuous fiber and foaming melt in the present invention. Using at least one of the above four reagents to pretreat and modify the fiber can improve the bonding between the continuous fiber and the foaming melt, allowing the continuous fiber to fully exert its reinforcing effect. When the temperature of the pretreatment liquid is 30~50℃, the compatibility between the continuous fiber and the foaming melt can be further improved. It is speculated that this is because the temperature is appropriate, and the film formed by the pretreatment liquid on the surface of the continuous fiber has higher uniformity. In a specific embodiment of the present invention, the solvent in the pretreatment liquid includes water.

[0017] The diameter of the foaming filament melt and the diameter of the continuous fiber itself also affect the interaction between the foamed skin and the continuous fiber core. Controlling these two diameters is equivalent to controlling the ratio between the continuous fiber and the foamed skin. A high or low ratio of continuous fiber will result in a part that cannot achieve both high strength and high precision. When the diameter of the continuous fiber is too low, the improvement in part strength is not significant. When the diameter of the continuous fiber is too high, the specific surface area of the fiber decreases, the contact area between the fiber and the foamed melt decreases, and the interaction between the two decreases, which also leads to a decrease in part strength.

[0018] In a specific embodiment of the present invention, the method for preparing continuous fiber reinforced 3D printed foam parts 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 motion bracket, a stacking platform, and a printer housing.

[0019] In a specific embodiment of the present invention, the adding of continuous fibers for co-extrusion in step S2 is achieved by introducing a continuous fiber feed port through an opening at a side end of an extrusion die of an extrusion unit.

[0020] In a specific embodiment of the present invention, the diameter of the foamed filament melt can be controlled to be 0.2-1.2 mm by adjusting the size of the extrusion die of the single-screw extruder to be 0.01-1.0 mm.

[0021] In a specific embodiment of the present invention, the coaxial co-extrusion described in step S2 refers to the melt formed by the pretreated continuous fibers and the molten polymer particles sharing an axis. In the extrusion process of the present invention, the molten polymer particles will be coated on the outside of the pretreated continuous fibers, and the melt formed by the continuous fibers and the molten polymer particles are approximately in shape of a cylinder and a hollow cylinder, respectively. The line connected by the centers of the circles at both 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 inner core is coaxial with the foamed cortex, wherein the foamed cortex is prepared by foaming the molten polymer particles and can also be approximated as a hollow cylinder.

[0022] Preferably, the immersion time in step S1 is 30 to 300 seconds.

[0023] Preferably, the continuous fibers in step S1 include PET (polyethylene terephthalate) fibers.

[0024] By using PET continuous fibers to construct the inner core of the foamed filament melt, 3D printed foamed parts with higher strength and precision can be obtained.

[0025] Preferably, the diameter of the continuous fiber in step S1 is 0.1-0.3 mm.

[0026] More preferably, the fineness of the continuous fiber in step S1 is 150-300 D.

[0027] Preferably, the melting and the coaxial co-extrusion 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 0~30°C, the temperature of the second heating section is 150~300°C, and the temperature of the third heating section is 200~390°C. The real-time temperature of the third heating section is higher than that of the second heating section.

[0028] By employing the aforementioned extrusion process, controlled foaming of the polymer feedstock can be achieved, further enhancing the bonding strength between the continuous fibers and the foamed cortex. Specifically, after the polymer particles containing the foaming agent are delivered to the screw structure in the first heating section, the particle temperature is relatively low, reducing foaming agent loss and ensuring stable material delivery. The particles containing the foaming agent begin to melt in the screw in the second heating section and are compacted by the screw structure, achieving densification between the particles and further preventing the escape of the foaming agent. The particles containing the foaming agent continue to melt and foam in the third screw section. The metering properties of the screw structure ensure stable delivery of the foamed melt to the extruder die, achieving controlled foaming at the moment of extrusion. The foamed cortex formed by controlled foaming has a uniform surface, allowing for full contact and compatibility with the continuous fibers, resulting in a larger contact area and fewer air gaps between the two, resulting in good interfacial bonding between the cortex and the core. As a result, the resulting article of the present invention can fully utilize the reinforcing properties of the fiber core and thus possess superior strength. At the same time, due to the controllable foaming, the present invention can further reduce the density while ensuring the strength of the product and achieve more functionality.

[0029] In a specific embodiment of the present invention, in step S2, the first heating section is connected to a temperature control component to control the temperature between 0°C and 30°C, wherein the temperature control component includes at least one of a cooling air system and a water cooling system. The polymer particles containing the foaming agent do not expand in the first screw structure.

[0030] In a specific embodiment of the present invention, the temperature control accuracy of the second heating section and the third heating section in step S2 is 0.5-5°C, preferably 1-3°C.

[0031] 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 in step S2 is 0.1-1.5 s, preferably 0.2-1.0 s, and more preferably 0.3-0.8 s.

[0032] Preferably, the diameter of the foamed wire melt in step S2 is 0.3-0.5 mm.

[0033] When the diameter of the foamed filament 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 filament melt. The above adjustment can further improve the precision of the product.

[0034] More preferably, the thickness of the foamed skin layer in the foamed wire melt in step S2 is 0.08-0.3 mm.

[0035] Preferably, the speed of the coaxial coextrusion in step S2 is 1-3 kg / h.

[0036] In a specific embodiment of the present invention, the screw speed of the single-screw extruder in step S2 is 10-50 rpm.

[0037] Preferably, before melting the polymer particles containing a foaming agent in step S2, the step of subjecting the polymer particles containing a foaming agent to a low-temperature treatment is further included, wherein the low-temperature treatment is performed at a temperature of -40°C to 0°C and a humidity of 1% to 30%. The present invention does not impose a limitation on the duration of the low-temperature treatment; it is sufficient that the temperature of the raw material particles is substantially consistent with the ambient temperature. The low-temperature treatment can help prevent the loss of the foaming agent.

[0038] 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 %.

[0039] 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 circle, an ellipse, and a wedge, 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.

[0040] Preferably, the polymer particles containing a foaming agent in step S2 include the following raw materials calculated by mass:

[0041] 80-100 parts of polymer, 0.5-10 parts of foaming agent, 0-10 parts of nucleating agent, 0-0.5 parts of antioxidant.

[0042] Preferably, the polymer includes at least one of an amorphous polymer, a semi-crystalline polymer, a crystalline polymer, and a thermoplastic elastomer.

[0043] More preferably, the polymer has a melting point of 70-400° C. and a hardness of Shore 30A-85D.

[0044] More preferably, the amorphous polymer includes at least one of polystyrene (PS), polymethyl methacrylate (PMMA), polyetherimide (PEI), polyimide (PI), and polysulfone (PSF).

[0045] More preferably, the semi-crystalline polymer includes at least one of polyethylene terephthalate (PET), polylactic acid (PLA), and polyetheretherketone (PEEK).

[0046] More preferably, the crystalline polymer includes at least one of polyethylene (PE), polypropylene (PP), and nylon (PA).

[0047] More preferably, the thermoplastic elastomer includes at least one of polyurethane (PU), polyester elastomer (TPEE), and nylon elastomer (PEBA).

[0048] Preferably, the antioxidant includes at least one of an amine antioxidant, a phosphorus antioxidant, and a thiol antioxidant.

[0049] Preferably, the nucleating agent includes at least one of calcium carbonate, talc, mica, montmorillonite, nano-silica, carbon black, and carbon nanotubes.

[0050] Preferably, the foaming agent includes at least one of a fluid foaming agent and a solid foaming agent.

[0051] In a specific embodiment of the present invention, the polymer particles containing a blowing agent described in step S2 are prepared by blending polymer particles with a blowing agent. When the blowing agent is a fluid, the polymer particles are blended with the blowing agent by impregnation. When the blowing agent is a solid, a masterbatch of at least one of polyethylene (PE) and ethylene-vinyl acetate (EVA) is used, mixed with the solid blowing agent, and then blended with the polymer particles. The purpose of adding the masterbatch is to increase the particle size of the solid blowing agent, as solid blowing agents typically have a small particle size, which is not conducive to foaming.

[0052] More preferably, the fluid blowing agent comprises a supercritical fluid.

[0053] More preferably, the supercritical fluid includes at least one of CO2, N2, alkanes, and hydrogenated chlorofluorocarbons (HCFCs).

[0054] More preferably, the solid foaming agent includes at least one of expandable microspheres, carbonates, N,N'-dinitrosopentamethylenetetramine, and azodicarbonamide.

[0055] More preferably, the particle size of the nucleating agent is 0.05-5 μm.

[0056] 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.

[0057] In a specific embodiment of the present invention, the printing temperature of the 3D printing in step S3 is the temperature of the extrusion die of the single-screw extruder in step S1, that is, the extrusion temperature.

[0058] Preferably, the rotation angle of the 3D printing in step S3 is 0-80°, preferably 0-70°, and the rotation angular velocity is 0-5 rad / s, preferably 0-3 rad / s.

[0059] In a specific embodiment of the present invention, the stacking linear speed of the 3D printing in step S3 is 80-120 mm / s.

[0060] The present invention also protects a continuous fiber reinforced 3D printed foamed part prepared by the above preparation method.

[0061] The present invention also protects the application of the above-mentioned continuous fiber reinforced 3D printed foam parts in the fields of shoe materials, medical consumables, and handicrafts.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] The continuous fiber reinforced 3D printed foamed parts prepared by the preparation method provided by the present invention not only have good foaming performance, but also have a density not higher than 0.95g / cm 3 At the same time, the tensile strength can reach more than 400 MPa, which is 172% of the parts without the introduction of continuous fibers for reinforcement. In addition, the parts provided by the present invention have a dimensional error of less than 3%, indicating that the method of the present invention can also take into account the accuracy of the parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 A schematic diagram of the 3D printing device of the present invention, wherein the fiber feed port is introduced into the side opening of the extrusion die. The reference numbers are as follows: 1. Raw material bin, 2. Metering screw, 3. Air-cooled temperature control system, 4. Delivery hose, 5. Temperature control system, 6. Heating jacket, 7. Micro-extrusion die, 8. Continuous fiber feed gear, 9. Motion bracket, 10. Fiber filament roll, 11. Stacking platform, 12. Printer housing.

[0065] Figure 2 Detailed schematic diagram of the extrusion die of the 3D printing device of the present invention. Reference numerals are as follows: 13, polymer melt containing a blowing agent, 14, micro-extrusion die, 15, continuous fiber, 16, continuous fiber-reinforced polymer foam melt. DETAILED DESCRIPTION

[0066] The present invention will be further described below with reference to specific embodiments. However, these examples do not limit the present invention in any way. Unless otherwise noted, the raw materials and reagents used in the examples are conventionally purchased. The raw material information used in each example and comparative example is as follows (all references to hardness refer to Shore hardness):

[0067] Amorphous polymer A:

[0068] Polystyrene PS, brand GPPS158K, from BASF-YPC.

[0069] Semi-crystalline polymer B:

[0070] Polyetheretherketone PEEK, brand 1000, Mitsubishi Chemical.

[0071] Thermoplastic Elastomer C:

[0072] Thermoplastic polyurethane TPU, hardness 60A, BASF, Germany.

[0073] Foaming agent:

[0074] Expandable microspheres, commercially available.

[0075] Nucleating agent:

[0076] Polystyrene, average particle size 2 μm, commercially available.

[0077] Antioxidants:

[0078] Mercaptan antioxidant, commercially available.

[0079] Continuous fiber:

[0080] PET fiber, commercially available, with a strength of 4 cN / dtex and a fineness of 200D.

[0081] Aramid fiber, commercially available, with a strength of 20 cN / dtex and a fineness of 200D.

[0082] Cellulose fiber, commercially available, with a strength of 10 cN / dtex and a fineness of 250D.

[0083] Carbon fiber, commercially available, with a strength of 18 cN / dtex and a fineness of 150D.

[0084] PTFE (polytetrafluoroethylene) fiber, commercially available, has a strength of 5.8 cN / dtex and a fineness of 180D.

[0085] Chopped Fiber:

[0086] PET fiber, commercially available, with a diameter of 0.2 mm.

[0087] Examples 1 to 12

[0088] This embodiment provides a series of methods for preparing continuous fiber reinforced 3D printed foam parts with different processing parameters and raw materials, including the following steps:

[0089] S1. The continuous fiber was immersed in a pretreatment solution at a temperature of 40°C for 2 min and then dried to obtain a pretreated continuous fiber; the continuous fiber was PET fiber with a diameter of 0.1 to 0.9 mm; the pretreatment solution included polydopamine at a concentration of 50 wt%, and the solvent was water;

[0090] S2. The polymer particles containing the foaming agent are subjected to low-temperature treatment at -20°C and 1% humidity until the particle temperature reaches -20°C, the particles are passed into the extrusion unit of the 3D printing equipment to melt the polymer particles containing the foaming agent, and the pretreated continuous fibers obtained in step S1 are added for coaxial co-extrusion to obtain a foamed filament melt, wherein the foamed filament melt contains a continuous fiber inner core and a foamed skin wrapped around the surface of the inner core, and has a diameter of 0.2-1.2 mm; the melting and the coaxial co-extrusion are carried out using a single-screw extruder, and 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, and 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 speed of the single-screw extruder is 25 rpm;

[0091] S3. The foamed wire melt obtained in step S1 is 3D printed according to the planned path to obtain a continuous fiber-reinforced 3D printed foamed part;

[0092] The above preparation method is carried out in a 3D printing device whose extrusion unit includes a single-screw extruder, and the 3D printing device includes the following functional units: a feeding unit, an extrusion unit, a printer motion bracket, a stacking platform, and a printer housing; the side end opening of the extrusion die of the single-screw extruder is introduced into the continuous fiber feed port, such as Figures 1 and 2 As shown. Figure 2 The polymer melt 13 containing the foaming agent will sequentially undergo a cell nucleation stage and a cell growth stage during the extrusion process, and then obtain a continuous fiber-reinforced polymer foam melt after extrusion.

[0093] In this embodiment, the following components are included by weight: 100 parts of polymer, 5 parts of foaming agent, 5 parts of nucleating agent, and 0.3 parts of antioxidant.

[0094] The specific processing parameters and raw materials for preparation in this embodiment are shown in Table 1 below:

[0095] Table 1. Specific processing parameters in Examples 1 to 12

[0096]

[0097] Example 13

[0098] A method for preparing a continuous fiber reinforced 3D printed foamed part, which differs from Example 5 only in that:

[0099] The coextrusion speed in step S2 is 0.8 kg / h.

[0100] Example 14

[0101] A method for preparing a continuous fiber reinforced 3D printed foamed part, which differs from Example 5 only in that:

[0102] The coextrusion speed in step S2 is 3.2 kg / h.

[0103] Example 15

[0104] A method for preparing a continuous fiber reinforced 3D printed foamed part, which differs from Example 5 only in that:

[0105] In step S2, the temperature of the first heating section is 100°C.

[0106] Example 16

[0107] A method for preparing a continuous fiber reinforced 3D printed foamed part, which differs from Example 5 only in that:

[0108] The continuous fiber in step S1 is PTFE fiber.

[0109] Comparative Example 1

[0110] A method for preparing a 3D printed foamed part, which differs from Example 5 only in that:

[0111] In step S2, no continuous fiber is introduced, that is, the extrusion die of the single-screw extruder in the 3D printing device is not opened at the side end.

[0112] Comparative Example 2

[0113] A method for preparing a continuous fiber reinforced 3D printed foamed part, which differs from Example 5 only in that:

[0114] 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.

[0115] Comparative Example 3

[0116] A method for preparing a continuous fiber reinforced 3D printed foamed part, which differs from Example 5 only in that:

[0117] The diameter of the continuous fiber in step S1 is 1.1 mm, and the diameter of the foamed wire melt in step S2 is 1.2 mm.

[0118] Comparative Example 4

[0119] A method for preparing a short fiber reinforced 3D printed foamed part, which differs from Example 5 only in that:

[0120] In step S2, polymer particles containing a foaming agent are blended with chopped fibers, and then melt-extruded; no continuous fibers are introduced during extrusion, that is, the extrusion die of the single-screw extruder in the 3D printing device is not opened on the side.

[0121] Comparative Example 5

[0122] A method for preparing a continuous fiber reinforced 3D printed foamed part, which differs from Example 5 only in that:

[0123] The continuous fibers in step S1 are carbon fibers.

[0124] Comparative Example 6

[0125] A method for preparing a continuous fiber reinforced 3D printed foamed part, which differs from Example 5 only in that:

[0126] The continuous fiber in step S1 is aramid fiber.

[0127] Comparative Example 7

[0128] A method for preparing a continuous fiber reinforced 3D printed foamed part, which differs from Example 5 only in that:

[0129] The continuous fibers in step S1 are cellulose fibers.

[0130] Comparative Example 8

[0131] A method for preparing a continuous fiber reinforced 3D printed foamed part, which differs from Example 5 only in that:

[0132] No preprocessing is performed in step S1.

[0133] Comparative Example 9

[0134] A method for preparing a continuous fiber reinforced 3D printed foamed part, which differs from Example 5 only in that:

[0135] The pretreatment solute in step S1 is maleic anhydride grafted polypropylene.

[0136] Comparative Example 10

[0137] A method for preparing a continuous fiber reinforced 3D printed foamed part, which differs from Example 5 only in that:

[0138] The pretreatment temperature in step S1 is 10°C.

[0139] Performance Testing

[0140] Sample preparation: 3D printing produces a sample with a size of 30×30×1.2mm, an "X"-shaped filling pattern, and a filling density of 30%.

[0141] Tensile breaking strength test: measured by a tensile testing machine.

[0142] Dimensional error measurement: measured by caliper.

[0143] Density test: Tested by density meter.

[0144] Processing behavior measurement: measured by visual observation.

[0145] Part appearance measurement: measured by visual observation.

[0146] The specific test data are shown in Table 2 below:

[0147] Table 2. Performance test data of 3D printed foam parts obtained in Examples and Comparative Examples

[0148]

[0149]

[0150]

[0151] According to the data in Table 2 above, the tensile strength of the continuous fiber reinforced 3D printed foamed parts prepared by the preparation method provided by the present invention can reach more than 400 MPa, which is 172% of the parts without continuous fiber reinforcement (Comparative Example 1). This shows that the method of the present invention can greatly improve the strength of the 3D foamed parts. At the same time, the parts provided by the present invention have a dimensional error of less than 3%, indicating that the method of the present invention can also take into account the accuracy of the parts. In addition, the parts of the present invention also have a tensile strength of not more than 0.95 g / cm 3 High density and excellent foaming performance.

[0152] According to Examples 5-10, the diameter of the foamed filament melt in step S2 is higher (Examples 7, 9-10), resulting in a decrease in the overall performance of the resulting product. Therefore, the present invention preferably has a diameter of 0.3-0.5 mm for the foamed filament melt in step S2. According to Example 11, excessively high foamed skin thickness also leads to decreased performance. Therefore, the present invention preferably has a thickness of 0.08-0.3 mm for the foamed skin layer in the foamed filament melt. 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), resulting in an increase in the density and a decrease in the strength of the resulting product. Therefore, the present invention preferably has a diameter of 0.1-0.3 mm for the continuous fiber.

[0153] According to Examples 5, 13, and 14, higher coextrusion speeds lead to decreased dimensional accuracy (Example 14), while lower coextrusion speeds result in decreased strength and increased density of the resulting part (Example 13). According to Example 15, using a conventional extrusion process (with temperatures exceeding 100°C in the first heating stage) can compromise the strength and precision of the part. As can be seen from Examples 5 and 16, the preparation method provided by the present invention, when using PET fiber as the core of the foamed filament melt, produces superior part performance, presumably due to the improved compatibility between PET fiber and the foamed filament melt.

[0154] According to Comparative Examples 1 and 4, the performance of the resulting parts was poor when continuous fibers were not introduced (Comparative Example 1) or chopped fibers were introduced (Comparative Example 2). Including chopped fibers as reinforcement did not significantly improve the strength of the parts, and instead resulted in a decrease in dimensional accuracy, leading to a downward trend in the strength of the parts.

[0155] According to Comparative Examples 2-3, if the diameter of the continuous fiber is too high or too low, the performance of the obtained product will be reduced. Among them, if the diameter of the continuous fiber is too small (Comparative Example 2), the reinforcement effect is not obvious, and it is easy to cause unstable wire feeding, which in turn affects the uniformity of the co-extruded foamed filament melt, resulting in large dimensional deviations and more defects in the product, further reducing the tensile strength; if the diameter of the continuous fiber is too large (Comparative Example 3), the cortex is relatively thin, and the continuous fiber is easily affected by the high temperature of the extrusion port during the extrusion process, resulting in fiber melting deformation (appearing as melting deformation of the foamed filament melt), and cannot be extruded normally. At the same time, the rigidity of the fiber is too high, resulting in poor interface adhesion, low molding accuracy, more defects between interfaces, and low strength.

[0156] 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 result in a decrease in precision, thereby affecting the improvement in strength achieved by the fibers.

[0157] According to Comparative Examples 8 to 10, the pretreatment step and its conditions also have an important impact on the performance of the product. No pretreatment, or too low a pretreatment temperature or inappropriate solute will lead to a decrease in the compatibility between the continuous fiber and the foaming melt, thereby affecting the performance.

[0158] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a continuous fiber reinforced 3D printed foamed part, characterized in that: The steps include: S1. Immersing a continuous fiber in a pretreatment solution at a temperature of 30-50°C and drying the pretreated continuous fiber to obtain a pretreated continuous fiber; the continuous fiber has a strength of 1-8 cN / dtex and a diameter of 0.1-0.9 mm; the pretreatment solution comprises at least one solute selected from maleic anhydride, polydopamine, tetrahydrofuran, and acetone; S2. Melting the polymer particles containing the foaming agent, adding the pretreated continuous fiber obtained in step S1 and coaxially coextruding to obtain a foamed filament melt, wherein the diameter of the foamed filament melt is 0.2 to 1.2 mm; the foamed filament melt comprises an inner core and a foamed skin wrapped around the surface of the inner core, wherein the inner core is a continuous fiber; S3. The foamed wire melt obtained in step S1 is 3D printed according to the planned path to obtain a continuous fiber-reinforced 3D printed foamed part; The melting and coaxial co-extrusion in step S2 are performed using a single-screw extruder, which includes a first heating section, 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., and the temperature of the third heating section is 200-390° C. The real-time temperature of the third heating section is higher than that of the second heating section. The diameter of the foamed wire melt in step S2 is 0.3-0.5 mm; The speed of the coaxial coextrusion in step S2 is 1-3 kg / h.

2. The method for preparing a continuous fiber reinforced 3D printed foamed part according to claim 1, wherein: The continuous fibers in step S1 include PET fibers.

3. The method for preparing a 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 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.

4. The method for preparing a continuous fiber reinforced 3D printed foamed part according to claim 3, wherein: Include at least one of the following (a) to (d): (a) the polymer comprises at least one of an amorphous polymer, a semi-crystalline polymer, a crystalline polymer, and a thermoplastic elastomer; (b) the antioxidant comprises at least one of an amine antioxidant, a phosphorus antioxidant, and a thiol antioxidant; (c) the nucleating agent comprises 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 a fluid foaming agent and a solid foaming agent.

5. The method for preparing a continuous fiber reinforced 3D printed foamed part according to claim 4, wherein: Include at least one of the following (e) to (k): (e) the amorphous polymer comprises at least one of polystyrene, polymethyl methacrylate, polyetherimide, polyimide, and polysulfone; (f) the semi-crystalline polymer comprises at least one of polyethylene terephthalate, polylactic acid, and polyetheretherketone; (g) the crystalline polymer comprises at least one of polyethylene, polypropylene, and nylon; (h) the thermoplastic elastomer comprises at least one of polyurethane, polyester elastomer, and nylon elastomer; (i) the fluid foaming agent comprises a supercritical fluid; (j) the solid foaming agent comprises at least one of expandable microspheres, carbonates, N,N'-dinitrosopentamethylenetetramine, and azodicarbonamide; (k) The particle size of the nucleating agent is 0.05-5 μm.

6. A continuous fiber reinforced 3D printed foamed part prepared by the preparation method according to any one of claims 1 to 5.

7. Application of the continuous fiber reinforced 3D printed foamed parts according to claim 6 in the fields of footwear, medical consumables, and handicrafts.

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