Composite material for 3D printing, 3D printing filament and FFF printing method

Abstract

A composite material for 3D printing, a 3D printing filament and an FFF printing method. The composite material comprises a continuous matrix phase and a fiber dispersed phase distributed in the continuous matrix phase, wherein the continuous matrix phase is made of a first crystalline polymer, and the fiber dispersed phase is made of a second crystalline polymer; and the fiber dispersed phase is of a micro-nano fiber structure, and the melting point of the second crystalline polymer is higher than that of the first crystalline polymer. The composite material for 3D printing is further subjected to single-screw extrusion to form a filament, and the 3D printing filament is then subjected to FFF printing, wherein the extrusion temperature and the printing temperature are both higher than the melting point of the first crystalline polymer, but lower than the melting point of the second crystalline polymer. By introducing the high-melting-point fiber dispersed phase into the dispersion matrix phase by means of an in-situ fibrillation processing technique, the composite material is obtained; moreover, a specially designed temperature process strategy is utilized, thereby allowing the printing material to have both improved heat resistance during printing and good warping resistance.

Description

Composite materials and 3D printing filaments for 3D printing, as well as FFF printing methods

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority and benefits to the Chinese patent application with patent application number 202311826315.7 filed with the State Intellectual Property Office of China on December 27, 2023, and entitled “Composite materials for 3D printing, 3D printing wires, and FFF printing method”, and incorporates the entire text of the patent application into this disclosure by reference. Technical Field

[0003] The present disclosure relates to the field of 3D printing technology, and in particular to a composite material for 3D printing, a 3D printing filament, and an FFF printing method. Background Art

[0004] Material-Extrusion-Based 3D Printing (ME-3DP) is one of the most mainstream forms of polymer additive manufacturing technology. Its principle is to melt the polymer material at high temperature to achieve melt fluidity, and then use a certain metered method to build up the material layer by layer. Within extrusion-based 3D printing, fused filament fabrication (FFF) is one of the mainstream technologies.

[0005] In FFF printing, some materials have poor heat resistance due to their low crystallinity, which limits their application scenarios. For example, polylactic acid (PLA) material is currently the most common printing material in FFF printing. Its excellent anti-warping properties, interlayer adhesion, and fully bio-based biodegradability make it the "best to use and most market-recognized" type of material. However, with the expansion of FFF printing applications, the low heat resistance of PLA material prints (heat softening temperature of about 60°C) has become one of its long-standing pain points. Specifically, the glass transition temperature T of PLA material is about 100°C. g About 60℃, melting temperature T m The temperature is about 150-180℃. In theory, PLA material has the potential to achieve heat resistance above 100℃. However, its crystallization ability is poor. Under normal FFF printing conditions, the crystallization rate is low and the crystallinity of the printed parts is low, resulting in its heat resistance of around 60℃, which can only meet some use scenarios with low requirements for material heat resistance. In addition, the poor crystallization ability and low T of PLA material g , which is also the source of its excellent warping resistance.

[0006] At present, several common technical routes to improve the heat resistance of PLA material prints are:

[0007] (1) Significantly improve the crystallization ability / crystallization rate of PLA materials.

[0008] This technical route is based on improving the crystallization ability of PLA materials, increasing the crystallization nucleation and growth rates during the printing process of PLA materials, so that the printed parts obtain a higher degree of crystallinity, thereby achieving an improvement in the heat resistance of the printed parts. During the FFF printing process, due to the existence of forced heat dissipation and air cooling, after the material is melted and extruded from the nozzle, the melt will undergo a rapid cooling process. The cooling rate in the initial stage is even as high as hundreds or thousands of ° C / s. During the high-speed cooling process, it is difficult for PLA materials to obtain a high degree of crystallinity. Moreover, even if the above-mentioned crystallization ability problem is solved, there will still be a problem of significantly reduced warping resistance due to the formation of a high degree of crystallinity during the printing process of PLA materials. The mechanism is that during the cooling / cooling and shaping process of the polymer melt, the formation of a crystal structure causes a large degree of volume shrinkage of the material, which generates internal stress and causes warping of the printed parts.

[0009] (2) PLA material is blended and modified with other materials such as high heat resistance.

[0010] PLA material and other high T g Or high crystallinity materials are blended and modified to prepare blended alloy materials. The improvement of heat resistance of this technical route generally depends on the addition of high heat-resistant components. If it is too low, the heat resistance effect will not be significantly improved. If it is too high, the adhesion between printed layers will be seriously reduced due to the multi-phase system. At the same time, high T g The excessive introduction of high-crystalline materials will also lead to a decrease in the material's resistance to warping.

[0011] (3) Annealing and crystallization process of printed parts.

[0012] T g is the critical temperature at which polymer molecular segments have the ability to move: T g Below the temperature, the polymer molecular chain segments are in a "frozen" state and have no ability to move; T g Above the temperature, the polymer molecular chain segments "thaw" and have the ability to move. The polymer crystallization process is the process of orderly arrangement of molecular chains, which requires the chain segments to have the ability to move. Therefore, at T g Temperatures above 100°C are the objective temperature conditions for polymer crystallization. One of the technical approaches to improve the heat resistance of PLA prints is to perform T g Annealing heat treatment above temperature, its mechanism is to heat the PLA printed part to T g The above process makes the PLA molecular chain segments have the ability to move, crystallize, improve the crystallinity of the printed parts, and then improve the heat resistance, which is called the "annealing crystallization process". However, in the annealing crystallization process, due to the temperature at T gAs the molecular chains gain mobility, the printed parts also risk deformation during the crystallization process. Furthermore, adding the annealing crystallization process also increases process costs.

[0013] In view of this, the present disclosure is proposed.

[0014] Summary of the Invention

[0015] The purpose of the present disclosure is to provide a composite material for 3D printing, a 3D printing filament, and an FFF printing method to improve the technical pain points of achieving high heat resistance of printing materials in the above-mentioned FFF printing.

[0016] The present disclosure is achieved as follows:

[0017] In a first aspect, the present disclosure provides a composite material for 3D printing, comprising a continuous matrix phase and a fiber dispersed phase distributed in the continuous matrix phase, wherein the continuous matrix phase is made of a first crystalline polymer, and the fiber dispersed phase is made of a second crystalline polymer; wherein the fiber dispersed phase is a micro-nano-scale fiber structure, and the melting point of the second crystalline polymer is higher than the melting point of the first crystalline polymer.

[0018] Optionally, the melting point of the second crystalline polymer is higher than the melting point of the first crystalline polymer by more than 30°C; and / or the mass percentage of the fiber dispersed phase in the composite material for 3D printing is 5% to 30%; and / or the fiber structure is mainly a fiber network structure formed by interweaving fibers with an aspect ratio greater than 10.

[0019] Optionally, the first crystalline polymer is polylactic acid; and / or the second crystalline polymer includes a crystalline polyester material and a crystalline polyamide material.

[0020] In a second aspect, the present disclosure also provides a method for preparing the above-mentioned composite material for 3D printing, which comprises: treating a blend of a first crystalline polymer and a second crystalline polymer by an in-situ fiber-forming technology, so that the second crystalline polymer forms a fiber dispersed phase in the first crystalline polymer.

[0021] In a third aspect, the present disclosure further provides a method for preparing a 3D printing filament, which comprises subjecting the above-mentioned composite material for 3D printing to single-screw extrusion to form a filament; wherein the extrusion temperature is greater than the melting point of the first crystalline polymer and less than the melting point of the second crystalline polymer.

[0022] In a fourth aspect, the present disclosure further provides a 3D printing wire, which is prepared by the above-mentioned method for preparing the 3D printing wire.

[0023] In a fifth aspect, the present disclosure also provides the application of the above-mentioned 3D printing composite materials or 3D printing wires in extrusion 3D printing technology.

[0024] In a sixth aspect, the present disclosure further provides an FFF printing method, comprising: performing FFF printing using the above-mentioned 3D printing filament, wherein the printing temperature is greater than the melting point of the first crystalline polymer and less than the melting point of the second crystalline polymer.

[0025] In a seventh aspect, the present disclosure further provides an FFF printed product, which is printed by the above-mentioned FFF printing method; optionally, the Vicat heat resistance temperature of the FFF printed product is greater than 100°C.

[0026] The present disclosure has the following beneficial effects: by using a first crystalline polymer (such as polylactic acid) with a lower melting point as a continuous matrix phase, and a second crystalline polymer with a higher melting point as a fiber dispersed phase, and the fiber dispersed phase is a micro-nano fiber structure. It is used as the main material for 3D printing, and printed below the melting point temperature of the second crystalline polymer. The second crystalline polymer as the dispersed phase can preserve the micro-nano fiber structure while not destroying the crystalline structure, and is directly introduced into the printed part. The dispersed phase part will not experience warping behavior caused by crystalline internal stress. At the same time, due to the high specific surface area of ​​the fiber dispersed phase, a significant crystalline heterogeneous nucleation effect is achieved, which promotes the improvement of the crystallinity of the first crystalline polymer (such as polylactic acid) print. Thereby, the printed product printed with a material with poor heat resistance (such as polylactic acid) as the main material has excellent heat resistance and warping resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0028] FIG1 is a schematic diagram of the process principle of in-situ fiber-forming composite materials;

[0029] FIG2 shows a schematic diagram of a warpage-resistant printing model used in accordance with some embodiments of this specification;

[0030] FIG3 is a micrograph of the microfiber structure in the wire of Example 1 of the present disclosure;

[0031] FIG4 is a diagram showing the warpage test results of the 3D printed product of Example 1 of the present disclosure;

[0032] FIG5 is a micrograph of the microfiber structure in the wire of Example 2 of the present disclosure;

[0033] FIG6 is a diagram showing the warpage test results of the 3D printed product of Example 2 of the present disclosure;

[0034] FIG7 is a micrograph of the microfiber structure in the wire of Example 3 of the present disclosure;

[0035] FIG8 is a diagram showing the warpage test results of the 3D printed product of Example 3 of the present disclosure;

[0036] FIG9 is a diagram showing the warpage test results of the 3D printed product of Comparative Example 1 of the present disclosure;

[0037] FIG10 is a diagram showing the warpage test results of the 3D printed product of Comparative Example 2 of the present disclosure;

[0038] FIG11 is a graph showing the warpage test results of the 3D printed product of Comparative Example 3 of the present disclosure. DETAILED DESCRIPTION

[0039] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0040] The following is a detailed description of a 3D printing composite material, a 3D printing filament, and an FFF printing method provided by the present disclosure.

[0041] Some embodiments of the present disclosure provide a composite material for 3D printing, which includes a continuous matrix phase and a fiber dispersed phase distributed in the continuous matrix phase, wherein the material of the continuous matrix phase is a first crystalline polymer, and the material of the fiber dispersed phase is a second crystalline polymer; wherein the fiber dispersed phase is a micro-nano-scale fiber structure, and the melting point of the second crystalline polymer is higher than the melting point of the first crystalline polymer.

[0042] It should be noted that the composite material of the above-described embodiment is intended for 3D printing. Therefore, the material used for its continuous matrix phase is suitable for 3D printing, such as polylactic acid. The inventors, through research on materials used for 3D printing, discovered that some commonly used semi-crystalline polymer materials, due to their poor crystallinity, only have heat resistance temperatures around their glass transition temperature (Tg), failing to realize their theoretical heat resistance potential close to their melting point.

[0043] Therefore, the inventors conducted further research and practice on this basis, and creatively proposed to use common 3D printing materials (such as polylactic acid) as the continuous matrix phase, to form a micro-nano fiber structure in the continuous matrix phase, and the melting point of the fiber structure is higher than the melting point of the continuous matrix phase. The composite material for 3D printing based on this structure is printed below the melting point temperature of the fiber structure material (i.e., the second crystalline polymer). The fiber structure material as the dispersed phase can preserve the micro-nano fiber structure while not destroying the crystal structure. At the same time, the high specific surface area of ​​the fiber dispersed phase is utilized to play a significant role in crystallization heterogeneous nucleation, thereby promoting the improvement of the crystallinity of the continuous matrix phase (i.e., the first crystalline polymer) print. And it is different from the existing method of adding high T g Or blending and modifying with highly crystalline materials, which fundamentally improves the crystallinity of the matrix phase and its heat resistance, independent of the added modified material itself. The high crystallinity and heat resistance of the micro-nano fiber structure itself have an anti-warping effect, which will provide a certain skeletal support for the continuous matrix phase. Therefore, the introduction of the fiber dispersed phase not only does not affect the material's warpage, but also can enhance the material's warpage resistance to a certain extent. In other words, the composite material for 3D printing has improved heat resistance and warpage resistance compared to existing alloy blend modified materials.

[0044] Furthermore, in order to ensure that the composite material for 3D printing has better usability, that is, during 3D printing, it is easy to select a temperature that is lower than the melting point of the second crystalline polymer and higher than the melting point of the first crystalline polymer as the printing temperature, so that at the printing temperature, the first crystalline polymer melts while the morphology of the second crystalline polymer is not affected. In some embodiments, the melting point of the second crystalline polymer is higher than the melting point of the first crystalline polymer by more than 30°C. For example, if the first crystalline polymer is polylactic acid, which generally has a melting point of 150-180°C, the second crystalline polymer is selected to have a melting point of 200°C or higher. In addition, it is preferred that the melting point of the second crystalline polymer is higher than the melting point of the first crystalline polymer by 30°C to 100°C.

[0045] It should be noted that the amount of fiber dispersed phase dispersed in the continuous matrix dispersed phase will have a certain impact on the processing performance and heat resistance enhancement performance of the material. If the content of the fiber dispersed phase is too little, it will not play a better role in crystallization heterogeneous nucleation, thereby resulting in the crystallinity of the 3D printed parts not being effectively improved; if the content of the fiber dispersed phase is too high, on the one hand, it will affect the printing performance of the matrix dispersed phase itself, and on the other hand, it will also affect the formation and uniform distribution of the fiber dispersed phase in the matrix dispersed phase, which is prone to agglomeration and affects the overall performance of the composite material. Therefore, in some embodiments, the mass percentage of the fiber dispersed phase in the composite material for 3D printing is 3% to 30%. For example, the mass percentage of the fiber dispersed phase in the composite material for 3D printing is 3%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%, etc. Preferably, the mass percentage of the fiber dispersed phase in the composite material for 3D printing is 3% to 20%, and more preferably, the mass percentage of the fiber dispersed phase in the composite material for 3D printing is 5% to 15%.

[0046] Furthermore, the fiber morphology of the dispersed phase also affects the heat resistance and warpage resistance of the composite material. In some embodiments, the fiber structure of the dispersed phase distributed within the continuous dispersed phase primarily comprises a fiber network structure, and inevitably, some of the fiber structure exists as a single fiber line structure. Theoretically, the greater the proportion of the fiber network structure, the better the performance, and the more uniform the fiber structure distribution, the better the performance.

[0047] It should be noted that the aforementioned micro-nanoscale fiber structure refers to the micro-nanoscale diameter of the dispersed fiber phase, typically ranging from tens of nanometers to hundreds of nanometers, or from a few micrometers to tens of micrometers. The high aspect ratio, high specific surface area, and excellent dispersion of the dispersed fiber phase at the micro-nanoscale enable it to form an intertwined microfiber network structure at a relatively low content of the dispersed fiber phase, thereby achieving an excellent reinforcement effect. In some embodiments, the fiber structure is primarily a fiber mesh structure formed by interweaving fibers with an aspect ratio greater than 10.

[0048] In some embodiments, the first crystalline polymer is polylactic acid. Polylactic acid is one of the most common materials for FFF printing, which is one of the mainstream technical forms in the current extrusion 3D printing technology. It has the feasibility that is most consistent with the above-mentioned embodiments of the present disclosure and can solve the long-standing technical pain points of the high heat resistance technical route of FFF printing of polylactic acid materials.

[0049] In some embodiments, the second crystalline polymer includes a crystalline polyester material and a crystalline polyamide material. For example, the second crystalline polymer can be selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycaprolactam (nylon 6), polyhexamethylene adipamide (nylon 66), and the like.

[0050] Based on the above, some embodiments of the present disclosure further provide a method for preparing a composite material for 3D printing in the above embodiment, which comprises: treating a blend of a first crystalline polymer and a second crystalline polymer by an in-situ fiber-forming technology, so that the second crystalline polymer forms a fiber dispersed phase in the first crystalline polymer.

[0051] In-situ fiberization technology refers to a fiber-reinforced material processing method in which, after blending multiple incompatible polymers, the dispersed phase in the two-phase system is stretched or sheared by applying an external force field, causing it to align along the direction of the external force and undergo fiberization, forming oriented micro-nano fibers in the continuous phase. This fiber-reinforced composite material, which forms a fiber phase "in situ" from the dispersed phase through a special processing technique, is vividly called an "in-situ Micro Fibrillation Composite" (iMFC). The schematic diagram of the principle is shown in Figure 1.

[0052] The in-situ fiber-forming technology can well obtain the composite material for 3D printing with the specific structure in the above embodiment, and the formed fiber dispersed phase is relatively evenly distributed in the continuous matrix phase.

[0053] Furthermore, it should be noted that the 3D printing composite materials and their preparation methods in the above embodiments are designed based on the material defects existing in the 3D printing process. A high-melting-point second phase component is introduced into the existing printing material (such as polylactic acid), and a composite material is prepared through an in-situ fiberization process. The composite material is then used to perform a 3D printing operation process to obtain a printed product with both improved printing heat resistance and excellent anti-warping properties.

[0054] Some embodiments of the present disclosure provide an FFF printing method, comprising: first processing the composite material for 3D printing in the above-mentioned embodiment into a 3D printing filament, and then using the 3D printing filament to perform FFF printing, wherein the printing temperature is greater than the melting point of the first crystalline polymer and less than the melting point of the second crystalline polymer.

[0055] Specifically, based on the above FFF printing method, some embodiments of the present disclosure also provide a method for preparing 3D printing filament, which includes single-screw extrusion of the 3D printing composite material described in the above embodiment to form the filament; wherein the maximum value of the extruder temperature range is greater than the melting point of the first crystalline polymer and less than the melting point of the second crystalline polymer. By selecting this extrusion temperature, the filament can be processed into a filament suitable for FFF printing without destroying the microfiber structure of the 3D printing composite material.

[0056] Some embodiments of the present disclosure further provide an FFF printed product, which is printed by the FFF printing method in the above embodiment.

[0057] In some embodiments, the FFF printed product obtained by the above FFF printing method has a Vicat heat resistance temperature greater than 100°C, preferably greater than 120°C, and more preferably greater than 150°C.

[0058] In addition, some embodiments of the present disclosure further provide applications of the 3D printing composite materials or 3D printing wires in the above embodiments in extrusion-type 3D printing technology, where the applications include but are not limited to FFF printing.

[0059] Based on the above statements, it can be seen that the ideas of the above technical solutions of this disclosure mainly include the following points:

[0060] (1) The 3D printing filament is printed below the melting point of the fiber dispersed phase. While "preserving" the fiber dispersed phase, i.e., the microfiber structure, the crystal structure is not destroyed. Instead, it is directly introduced into the printed part. The fiber dispersed phase part will not experience warping caused by internal crystallization stress.

[0061] (2) By utilizing the in-situ fibrillation of the dispersed phase, a high specific surface area of ​​micro-nanoscale fibers is formed, which achieves significant heterogeneous nucleation of crystals and promotes the improvement of the crystallinity of 3D printing substrates (such as polylactic acid) printed parts.

[0062] (3) The dispersed phase is in situ fibrillated to form a micro-nano fiber reinforcement phase, and a microfiber grid structure is formed at a low content, achieving excellent reinforcement effect and anti-warping of printed parts.

[0063] The resulting micro-nano fiber-reinforced composite material for 3D printing has high crystallinity and heat resistance, which contributes to its anti-warping properties. This results in a 3D printing material with both excellent heat resistance and excellent warping resistance.

[0064] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0065] The anti-warping printing test method in the embodiment of the present disclosure is as follows:

[0066] Under a preset target external environment, the 3D printing material of the target size is printed on a target base plate using a target process flow into a target cuboid target part of the target size (L×W×H), wherein the side of the target part contacting the target base plate is the bottom surface, and its length is L, width is W, and height is H. After the cuboid part cools down, the heights of the four corners of the bottom surface of the cuboid part separated from the target base plate (that is, the distances from the four corners to the highest point of the target base plate) are measured, and the average value h is calculated. The warpage value of the 3D material is then defined as: the h value divided by the height H of the target part, that is, calculated using the following formula:

[0067] Obviously, given a constant L, W, and H, the smaller the average height h of the four corners of the bottom surface of the cuboid after cooling, the less deformation and warpage the part experiences during cooling. In this specification, the warpage resistance of a 3D printed material can be measured by the deformation produced during the printing process. The less warpage a 3D printed product experiences after printing, the better the warpage resistance of the 3D printed material.

[0068] It is understandable that for the same material, under different standard sizes and different external cooling environments, the cooling speed and cooling uniformity of the material are different, so the warpage rate may also be different.

[0069] FIG2 shows a schematic diagram of a target printing model used in some embodiments of this specification. The target dimensions of the target part in the target printing model may be L = 150 mm, W = 9.6 mm, and H = 20 mm. In this case, the following formula is used for calculation:

[0070] According to some embodiments of the present application, the preset target external environment may include: PLA filament with a diameter of 1.75 mm ± 0.05 mm, a nozzle diameter of 0.4 mm, slicing parameters of 0.4 mm line width, 0.2 mm layer height, 13 shells, and a printing speed of 100 mm / s. Furthermore, the printing temperature in this embodiment is adjusted based on the material type and extrusion characteristics. For example, the printing temperature for PLA is 190-230°C, and the base plate temperature is 30-60°C.

[0071] For example, if the target part (printed part) has a length of 150 mm and a height of 20 mm, and the average warpage height h of the four corners after cooling is 1 mm, the warp rate is calculated to be 5%.

[0072] Example 1

[0073] This embodiment provides an FFF printing method, which specifically includes the following steps:

[0074] 1) Preparation of in-situ fiberized composite materials for 3D printing.

[0075] With polylactic acid PLA as the matrix phase (melting point T m1 170℃), with polybutylene terephthalate PBT as the dispersed phase (fiber-forming phase) (melting point T m2 The temperature is 225° C.), wherein the mass content of the fiber-forming phase PBT in the formed 3D printing composite material is 10%.

[0076] After the above-mentioned PLA and PBT are mixed in a certain proportion, a twin-screw extrusion process is used for mixing at a processing temperature of 160-240°C. The extruded material strips are pulled, cooled and shaped in a normal temperature water tank, and pelletized by a pelletizer to prepare an in-situ fiber-forming composite material for 3D printing.

[0077] 2) Processing the prepared 3D printing composite material into wire.

[0078] The specific operation is: single-screw extrusion is performed at a temperature of 160-210°C to prepare the wire iMFC-Filament.

[0079] The fiber structure of the cross section of the obtained in-situ fiber-forming wire iMFC-Filament was observed under a microscope, and the microfiber structure is shown in Figure 3.

[0080] 3) Perform FFF printing test on iMFC-Filament.

[0081] The FFF-printed product was subjected to a warpage resistance test at 210°C, resulting in the printed product shown in Figure 4. The product is a rectangular parallelepiped with a length of 150 mm, a width of 9.6 mm, and a height of 20 mm. As shown in Figure 4, the printed product exhibited no warpage, demonstrating excellent warpage resistance.

[0082] At the same time, the printed product was subjected to a Vicat heat resistance test using GB / T 1633-2000 Vicat softening temperature (VST) of thermoplastics, the A120 method, a force of 10N, and a heating rate of 120°C / h. The Vicat heat resistance temperature of the printed product was measured to be 153.9°C, indicating good heat resistance.

[0083] It can be seen that the PLA-based iMFC printing material provided in this embodiment has both excellent printing anti-warping properties and heat resistance of printed parts.

[0084] Example 2

[0085] This embodiment provides an FFF printing method, which specifically includes the following steps:

[0086] 1) Preparation of in-situ fiberized composite materials for 3D printing.

[0087] With polylactic acid PLA as the matrix phase (same as Example 1, melting point T m1 170℃), with polybutylene terephthalate PBT as the dispersed phase (fiber-forming phase) (melting point T m2 The temperature is 225° C.), wherein the mass content of the fiber-forming phase PBT in the formed 3D printing composite material is 20%.

[0088] After the above-mentioned PLA and PBT are mixed in a certain proportion, a twin-screw extrusion process is used for mixing at a processing temperature of 160-240°C. The extruded material strips are pulled, cooled and shaped in a normal temperature water tank, and pelletized by a pelletizer to prepare an in-situ fiber-forming composite material for 3D printing.

[0089] 2) Processing the prepared 3D printing composite material into wire.

[0090] The specific operation is: single-screw extrusion is performed at a temperature of 160-210°C to prepare the wire iMFC-Filament.

[0091] The fiber structure of the cross section of the obtained in-situ fiber-forming wire iMFC-Filament was observed under a microscope, and the microfiber structure is shown in FIG5 .

[0092] 3) Perform FFF printing test on iMFC-Filament.

[0093] The FFF-printed product was subjected to a warpage resistance test at 210°C, resulting in the rectangular product shown in Figure 6: length L = 150 mm, width W = 9.6 mm, height H = 20 mm. As shown in Figure 6, the printed product exhibited no warpage, demonstrating excellent warpage resistance.

[0094] At the same time, the printed product was subjected to a Vicat heat resistance test using GB / T 1633-2000 Vicat softening temperature (VST) of thermoplastics, the A120 method, a force of 10N, and a heating rate of 120°C / h. The Vicat heat resistance temperature of the printed product was measured to be 167.3°C, indicating good heat resistance.

[0095] It can be seen that the PLA-based iMFC printing material provided in this embodiment has both excellent printing anti-warping properties and heat resistance of printed parts.

[0096] Example 3

[0097] This embodiment provides an FFF printing method, which specifically includes the following steps:

[0098] 1) Preparation of in-situ fiberized composite materials for 3D printing.

[0099] With polylactic acid PLA as the matrix phase (same as Example 1, melting point T m1 170℃), with polycaprolactam (nylon 6) PA6 as dispersed phase (fiber-forming phase) (melting point T m2 The fiber-forming phase PA6 has a mass content of 5% in the formed composite material for 3D printing.

[0100] After the above-mentioned PLA and PA6 are mixed in a certain proportion, a twin-screw extrusion process is used for mixing at a processing temperature of 160-240°C. The extruded material strips are pulled, cooled and shaped in a normal temperature water tank, and pelletized by a pelletizer to prepare an in-situ fiber-forming composite material for 3D printing.

[0101] 2) Processing the prepared 3D printing composite material into wire.

[0102] The specific operation is: single-screw extrusion is performed at a temperature of 160-210°C to prepare the wire iMFC-Filament.

[0103] The fiber structure of the cross section of the obtained in-situ fiber-forming wire iMFC-Filament was observed under a microscope, and the microfiber structure is shown in FIG7 .

[0104] 3) Perform FFF printing test on iMFC-Filament.

[0105] The FFF-printed product was subjected to a warpage resistance test at 210°C, resulting in the printed product shown in Figure 8. The product is a rectangular parallelepiped with a length of 150 mm, a width of 9.6 mm, and a height of 20 mm. As shown in Figure 8, the warpage rate of the printed product was 0.63%, demonstrating excellent warpage resistance.

[0106] At the same time, the printed product was subjected to a Vicat heat resistance test using GB / T 1633-2000 Vicat softening temperature (VST) of thermoplastics, the A120 method, a force of 10N, and a heating rate of 120°C / h. The Vicat heat resistance temperature of the printed product was measured to be 133.5°C, indicating good heat resistance.

[0107] It can be seen that the PLA-based iMFC printing material provided in this embodiment has both excellent printing anti-warping properties and heat resistance of printed parts.

[0108] Comparative Example 1

[0109] This comparative example uses the same PLA material as in Example 1 to prepare a 3D printing material.

[0110] PLA raw material particles were used and single-screw extrusion was performed under the same process conditions as in Example 1 to prepare PLA wires.

[0111] The same anti-warping printing test method as in Example 1 was used for testing. FIG9 shows a photo of the printed product. As shown in FIG9 , the printed product has no warping as a whole and has excellent anti-warping properties.

[0112] The Vicat softening temperature (VST) of thermoplastics according to GB / T 1633-2000 was determined using the A120 method. A force of 10 N and a heating rate of 120°C / h were used. The Vicat heat resistance temperature of the printed part was 61.7°C, indicating that the heat resistance of the 3D printing material prepared in this comparative example was relatively low.

[0113] It can be seen that compared with the material in Example 1, the PLA printing material provided in Comparative Example 1 cannot have both excellent printing anti-warping properties and print heat resistance.

[0114] Comparative Example 2

[0115] This comparative example uses the same PLA material as in Example 1, adding an organic hydrazide crystallization nucleating agent at a weight percentage of 1% relative to the weight of the polylactic acid material. The 3D printing material is prepared using the same twin-screw mixing process and single-screw extrusion wire processing process as in Example 1.

[0116] The same anti-warping printing test method as in Example 1 was used for testing. FIG10 shows a photo of the printed product. As shown in FIG10 , the printed product exhibits significant warping, and the warping rate obtained from the test is 17.3%. Compared with Examples 1, 2, and 3, the printed product exhibits poor anti-warping properties.

[0117] Under the same experimental conditions, the test showed that the Vicat heat resistance temperature of its printed parts was 145.3℃.

[0118] It can be seen that compared with the materials in the examples, the PLA printing material provided in Comparative Example 2 cannot have both excellent printing anti-warping properties and print heat resistance.

[0119] Comparative Example 3

[0120] In this comparative example, we used the in-situ fiber-forming composite material wire in Example 1 and changed the printing temperature process to conduct comparative tests.

[0121] The warpage resistance test was conducted at 240°C, resulting in the printed product shown in Figure 11. The product is a rectangular parallelepiped with a length of 150 mm, a width of 9.6 mm, and a height of 20 mm. As shown in Figure 11, the warpage rate of the printed product was 9.6%.

[0122] The Vicat softening temperature (VST) of thermoplastics was determined according to GB / T 1633-2000, using the A120 method, a force of 10 N, and a heating rate of 120°C / h. The Vicat heat resistance temperature of the printed part was found to be 122.5°C.

[0123] Compared with Example 1, when the printing temperature is greater than the melting point of the PBT fiber-forming phase, the microfiber structure is destroyed, resulting in a significant decrease in the warping resistance of the printed material and the heat resistance of the printed part, further verifying the technical effect of the present disclosure.

[0124] It can be seen that compared with the material in Example 1, the PLA printing material provided in Comparative Example 3 cannot have both excellent printing anti-warping properties and print heat resistance.

[0125] In summary, the embodiments of the present disclosure are based on the understanding of the FFF printing behavior of highly crystalline polymer materials. A high-melting-point second-phase component is introduced into the PLA material, and a PLA-based in-situ fiber-forming composite material iMFC is prepared through an in-situ fiber-forming processing technology. At the same time, a specially designed temperature process strategy is adopted to achieve both improved printing heat resistance and excellent warping resistance of the PLA material.

[0126] The foregoing description is merely a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present disclosure shall be included within the scope of protection of the present disclosure. Industrial Applicability

[0127] The present invention discloses a method of using a first crystalline polymer (such as polylactic acid) with a lower melting point as a continuous matrix phase and a second crystalline polymer with a higher melting point as a fiber dispersed phase, wherein the fiber dispersed phase is a micro-nano fiber structure. The method uses the first crystalline polymer (such as polylactic acid) with a lower melting point as a continuous matrix phase and a second crystalline polymer (such as polylactic acid) with a higher melting point as a fiber dispersed phase. The fiber dispersed phase is used as the main material for 3D printing and is printed below the melting point temperature of the second crystalline polymer. The second crystalline polymer as the dispersed phase can preserve the micro-nano fiber structure while not destroying the crystalline structure. The dispersed phase portion does not experience warping behavior caused by crystalline internal stress. At the same time, due to the high specific surface area of ​​the fiber dispersed phase, a significant crystalline heterogeneous nucleation effect is achieved, which promotes the improvement of the crystallinity of the printed part of the first crystalline polymer (such as polylactic acid). Thus, the printed material has both improved printing heat resistance and excellent anti-warping properties, and has a better industrial application prospect.

Claims

1. A composite material for 3D printing, characterized in that, It includes a continuous matrix phase and a fiber dispersed phase distributed in the continuous matrix phase. The material of the continuous matrix phase is a first crystalline polymer, and the material of the fiber dispersed phase is a second crystalline polymer; wherein, the fiber dispersed phase is a micro-nano fiber structure, and the melting point of the second crystalline polymer is higher than that of the first crystalline polymer.

2. The composite material for 3D printing according to claim 1, wherein The melting point of the second crystalline polymer is more than 30 °C higher than that of the first crystalline polymer.

3. The composite material for 3D printing according to claim 1 or 2, characterized in that, The mass percentage of the fiber dispersed phase in the composite material for 3D printing is 3% - 30%.

4. The composite material for 3D printing according to any one of claims 1 to 3, characterized in that, The fiber structure is mainly fibers with an aspect ratio greater than 10, and the fiber diameter is 0.1 - 50 μm.

5. The composite material for 3D printing according to any one of claims 1 to 4, characterized in that The first crystalline polymer is polylactic acid.

6. The composite material for 3D printing according to any one of claims 1 to 5, characterized in that, The second crystalline polymer includes a crystalline polyester material and a crystalline polyamide material.

7. The composite material for 3D printing according to claim 6, wherein, The second crystalline polymer is at least one of polyethylene terephthalate, polybutylene terephthalate, polycaprolactam or polyhexamethylene adipamide.

8. A method for preparing a composite material for 3D printing according to any one of claims 1 to 7, characterized in that, It includes: The blend of the first crystalline polymer and the second crystalline polymer is processed by an in-situ fibrillation technique so that the second crystalline polymer forms the fiber dispersed phase in the first crystalline polymer.

9. A method for preparing a 3D printing wire, characterized in that, It includes forming a wire by single-screw extrusion of the composite material for 3D printing according to any one of claims 1 - 7; wherein, the highest value of the extrusion temperature section is greater than the melting point of the first crystalline polymer and less than the melting point of the second crystalline polymer.

10. A 3D printing wire, characterized in that, It is prepared by the preparation method according to claim 9.

11. Application of the composite material for 3D printing according to any one of claims 1 - 7 or the 3D printing wire according to claim 10 in an extrusion-based 3D printing technique.

12. A method for FFF printing, characterized in that, It includes: Performing FFF printing using the 3D printing wire according to claim 10, wherein the printing temperature is greater than the melting point of the first crystalline polymer and less than the melting point of the second crystalline polymer.

13. A FFF printed article, characterized in that, It is printed by the FFF printing method according to claim 12.

14. The FFF printed article according to claim 13, wherein, The Vicat heat resistance temperature of the FFF printed product is greater than 100 °C.

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