Modified reinforced high-temperature-resistant polylactic acid composite material suitable for 3D printing as well as preparation method and application of modified reinforced high-temperature-resistant polylactic acid composite material

Abstract

The invention provides a modified reinforced high-temperature-resistant polylactic acid composite material suitable for 3D printing as well as a preparation method and application thereof, and belongs to the technical field of 3D printing. The polylactic acid composite material is prepared from the following raw materials in parts by weight: 80-100 parts of poly-L-polylactic acid, 1-20 parts of poly-D-polylactic acid, 5-15 parts of a toughening agent, 1-5 parts of a chain extender, 0-5 parts of a plasticizer, 0-0.5 part of a cross-linking agent, 0.5-5 parts of a compatilizer, 1-5 parts of nano filler and 0-20 parts of cellulose nanocrystals. The polylactic acid composite material provided by the invention not only can provide excellent mechanical properties and a stable printing effect in a fused deposition modeling technology, but also can meet the use requirements in a high-temperature environment, so that the application range of a 3D printing material is greatly widened, and powerful support is provided for further development of a 3D printing technology.

Description

Technical Field

[0001] This invention belongs to the field of 3D printing technology, specifically relating to a modified and reinforced high-temperature resistant polylactic acid composite material suitable for 3D printing, its preparation method, and its applications. Background Technology

[0002] With the rapid development of 3D printing technology, 3D printing materials have been widely used in various fields such as industry, medicine, aerospace, and construction. Fused deposition modeling (FDM) technology, as one of the most commonly used additive manufacturing processes, relies heavily on material properties that directly affect the quality, strength, and usability of printed objects. In FDM, material properties directly impact printing quality and efficiency, thus continuously raising the performance requirements for 3D printing materials. Polylactic acid (PLLA), as an environmentally friendly, low-cost, and easily processed thermoplastic material, has been widely used in 3D printing. However, the application of traditional PLA materials in 3D printing faces certain limitations, mainly due to its poor toughness, poor high-temperature resistance, and low flow rate during printing.

[0003] In recent years, to address the shortcomings of traditional PLLA materials in FDM technology, researchers have begun modifying them to improve their performance. Polylactic acid (PLLA) itself is a relatively rigid material, but its fracture toughness is low, making it prone to brittle fracture under stress. Therefore, the insufficient toughness of PLLA has been a bottleneck in 3D printing material research. To address this, many studies have attempted to improve its fracture toughness by combining it with high-toughness materials such as rubber and polyurethane. Furthermore, PLLA has poor high-temperature resistance, with a glass transition temperature (Tg) of approximately 60-65℃ and a melting point of 170-180℃, limiting its applicability in some high-temperature applications. To improve its high-temperature resistance, researchers have used composites with high-temperature stable materials such as polycarbonate and polyamide to increase the heat distortion temperature and melting point of PLLA. In addition, the poor flowability of PLLA in FDM technology is also a major drawback. FDM printing requires the material to be fully melted at high temperatures and possess good flowability to ensure a smooth printing process. However, traditional polylactic acid (PLA) materials are prone to nozzle clogging or decreased printing accuracy at high printing speeds. Therefore, improving the flowability of PLA materials to ensure stable nozzle output at high printing speeds is key to improving printing efficiency and quality.

[0004] In existing technologies, several studies have explored ways to improve the flow rate, toughness, and high-temperature resistance of polylactic acid (PLA) materials. For example, US patent application US20180293355A1 proposes a PLA composite material with enhanced toughness and heat resistance. This composite material significantly improves toughness by combining PLA with styrene-butadiene-styrene (SBS) rubber. Simultaneously, the addition of appropriate amounts of high-temperature resistant materials significantly increases the composite material's heat distortion temperature and melting point. The core innovation of this patent lies in the ability to ensure both good toughness and stability under high-temperature conditions through reasonable control of the composite ratio. Chinese patent application CN103992986A describes a PLA-based high-toughness composite material and its preparation method. This material significantly enhances the toughness and thermal stability of PLA by incorporating polyurethane elastomers with excellent toughness and high-temperature resistance, maintaining good printing results even with significantly increased printing speeds. The innovation of this patent lies in the introduction of polyurethane materials with high thermal stability and good compatibility, which significantly improves the melt flowability of polylactic acid (PLA) materials, adapting to the demands of higher-speed 3D printing. Furthermore, many other studies have explored the flowability of PLA materials in depth. For example, Chinese patent application CN105639482A proposes a PLA-based composite material for fused deposition modeling. This material significantly improves PLA flowability by incorporating a low-melting-point thermoplastic resin with good flowability. The advantage of this technology is that by rationally selecting the type and proportion of low-melting-point resin, the melting temperature range of the material can be effectively increased, ensuring smooth printing at high flow rates.

[0005] Building upon the aforementioned research, existing technologies still face several challenges, such as balancing the toughness, high-temperature resistance, and flowability of polylactic acid (PLA) materials to meet the demands of diverse applications. Currently, most research focuses on improving the various properties of PLA materials through physical composites, chemical modification, or the addition of functional fillers. However, achieving high-performance, low-cost, and easily prepared PLA materials remains a challenge in technological development. Therefore, developing a novel PLA-based 3D printing material with high toughness, high flow rate, and high temperature resistance has significant practical application value. Summary of the Invention

[0006] The purpose of this invention is to provide a modified and reinforced high-temperature resistant polylactic acid composite material suitable for 3D printing, its preparation method, and its applications.

[0007] This invention provides a polylactic acid composite material suitable for 3D printing, which is prepared from raw materials in the following weight ratio:

[0008] 80-100 parts by weight of poly(L-)polylactic acid, 1-20 parts by weight of poly(D-)polylactic acid, 5-15 parts by weight of toughening agent, 1-5 parts by weight of chain extender, 0-5 parts by weight of plasticizer, 0-0.5 parts by weight of crosslinking agent, 0.5-5 parts by weight of compatibilizer, 1-5 parts by weight of nanofiller, and 0-20 parts by weight of cellulose nanocrystals.

[0009] Furthermore, the aforementioned polylactic acid composite material is prepared from raw materials in the following weight ratio:

[0010] 85-95 parts by weight of poly(L-)polylactic acid, 15 parts by weight of poly(D-)polylactic acid, 10 parts by weight of toughening agent, 3 parts by weight of chain extender, 0-4 parts by weight of plasticizer, 0-0.4 parts by weight of crosslinking agent, 3 parts by weight of compatibilizer, 3 parts by weight of nanofiller, and 0-20 parts by weight of cellulose nanocrystals.

[0011] Furthermore, the aforementioned polylactic acid composite material is prepared from raw materials in the following weight ratio:

[0012] 85 parts by weight of poly(L-)polylactic acid, 15 parts by weight of poly(D-)polylactic acid, 10 parts by weight of toughening agent, 3 parts by weight of chain extender, 0-2 parts by weight of plasticizer, 0-0.2 parts by weight of crosslinking agent, 3 parts by weight of compatibilizer, 3 parts by weight of nanofiller, and 0-10 parts by weight of cellulose nanocrystals.

[0013] Preferably, the aforementioned polylactic acid composite material is prepared from raw materials in the following weight ratio:

[0014] 85 parts by weight of poly(L-)polylactic acid, 15 parts by weight of poly(D-)polylactic acid, 10 parts by weight of toughening agent, 3 parts by weight of chain extender, 2 parts by weight of plasticizer, 0.2 parts by weight of crosslinking agent, 3 parts by weight of compatibilizer, 3 parts by weight of nanofiller, and 10 parts by weight of cellulose nanocrystals.

[0015] Furthermore,

[0016] The toughening agent is selected from one or more of thermoplastic elastomers, thermoplastic polyurethane elastomers, polyolefin elastomers, polycaprolactone, ethylene-vinyl acetate copolymer, and polybutylene terephthalate;

[0017] And / or, the chain extender is selected from BASF ADR chain extenders;

[0018] And / or, the plasticizer is selected from acetylated tributyl citrate, triethyl citrate, or tributyl citrate;

[0019] And / or, the crosslinking agent is selected from benzoyl peroxide or dicumyl peroxide;

[0020] And / or, the compatibilizer is selected from POE-grafted maleic anhydride;

[0021] And / or, the nanofiller is selected from one or more of nano silica, nano calcium carbonate, or nano montmorillonite.

[0022] Furthermore,

[0023] The toughening agent is composed of polybutylene terephthalate and polyolefin elastomer, with a mass ratio of polybutylene terephthalate to polyolefin elastomer of 1:1.

[0024] And / or, the plasticizer is selected from tributyl acetylcitrate;

[0025] And / or, the crosslinking agent is selected from dicumyl peroxide;

[0026] And / or, the nanofiller is selected from nano-silica.

[0027] Furthermore, the aforementioned polylactic acid composite material is prepared from raw materials in the following weight ratio:

[0028] 85 parts by weight of poly(L-lactic acid), 15 parts by weight of poly(D-lactic acid), 5 parts by weight of polybutylene terephthalate-adipate, 5 parts by weight of polyolefin elastomer, 3 parts by weight of BASF ADR chain extender, 2 parts by weight of acetylsalicylic acid tributyl ester, 0.2 parts by weight of dicumyl peroxide, 3 parts by weight of POE-MAH, 3 parts by weight of nano-silica, and 10 parts by weight of cellulose nanocrystals.

[0029] The present invention also provides a method for preparing the aforementioned polylactic acid composite material, which includes the following steps:

[0030] (1) Weigh out the raw materials as described above;

[0031] (2) Mix poly(L-)-polylactic acid, poly(D-)-polylactic acid, toughening agent, compatibilizer, nanofiller, crosslinking agent, chain extender and plasticizer evenly to obtain a mixture;

[0032] (3) The mixture obtained in step (2) and cellulose nanocrystals are co-extruded and cooled to obtain polylactic acid composite material;

[0033] Preferably, in step (2), the mixing is carried out at a speed of 100 to 1000 rpm for a duration of 1 to 60 min.

[0034] And / or, in step (3), a twin-screw extruder is used for the blending extrusion, with a screw speed of 5 to 30 rpm, an extruder feed port temperature of 140 to 160°C, an extruder middle zone temperature of 170 to 185°C, and an extruder die head temperature of 190 to 200°C.

[0035] More preferably, in step (2), the mixing is carried out by stirring at a speed of 400 rpm for a duration of 10 min;

[0036] And / or, in step (3), a twin-screw extruder is used for the blending extrusion, the screw speed starts from 5 rpm and gradually increases to the maximum speed of 30 rpm, the feed port temperature of the twin-screw extruder is 160℃, the temperature of the middle area of ​​the extruder is 185℃, and the die head temperature of the extruder is 190℃.

[0037] The present invention also provides a method for preparing the aforementioned polylactic acid composite material, which includes the following steps:

[0038] (a) Weigh the raw materials as described above;

[0039] (b) Poly(L-)-polylactic acid, poly(D-)-polylactic acid and a crosslinking agent in a mass percentage of 15-18% were co-extruded to obtain a PLLA / PDLA composite.

[0040] (c) The PLLA / PDLA complex, toughening agent and compatibilizer are mixed and then pulverized into powder;

[0041] (d) Mix the powder, chain extender, plasticizer and nanofiller obtained in step (c) evenly to obtain elastomer microspheres;

[0042] (e) Poly(L-lactic acid), cellulose nanocrystals and elastomer microspheres obtained in step (d) are blended and extruded with a remaining mass percentage of 82-85% and cooled to obtain polylactic acid composite material;

[0043] Preferably,

[0044] In step (b), a twin-screw extruder is used for the blending extrusion, with a screw speed of 5 to 30 rpm, an extruder feed port temperature of 140 to 160°C, an extruder middle zone temperature of 170 to 185°C, and an extruder die head temperature of 190 to 200°C.

[0045] And / or, in step (d), the mixing is carried out by stirring at a speed of 100 to 1000 rpm for a time of 1 to 60 min;

[0046] And / or, in step (e), a twin-screw extruder is used for the blending extrusion, with a screw speed of 5 to 30 rpm, an extruder feed port temperature of 140 to 160°C, an extruder intermediate zone temperature of 170 to 185°C, and an extruder die head temperature of 190 to 200°C.

[0047] More preferably,

[0048] In step (b), a twin-screw extruder is used for the blending extrusion. The screw speed starts from 5 rpm and gradually increases to the maximum speed of 30 rpm. The feed port temperature of the twin-screw extruder is 160°C, the temperature of the middle area of ​​the extruder is 185°C, and the die head temperature of the extruder is 190°C.

[0049] And / or, in step (b), the obtained PLLA / PDLA composite is dried in a vacuum oven at 80°C to constant weight before use;

[0050] And / or, in step (c), the pulverization method is to first soak in liquid nitrogen and then pulverize it into powder, the particle size of which is 300 mesh;

[0051] And / or, in step (d), the mixing is performed by stirring at a speed of 400 rpm for a duration of 10 min;

[0052] And / or, in step (e), a twin-screw extruder is used for the blending extrusion, with the screw speed starting from 5 rpm and gradually increasing to the maximum speed of 30 rpm. The temperature at the feed port of the twin-screw extruder is 160°C, the temperature in the middle zone of the extruder is 185°C, and the temperature at the die head of the extruder is 190°C.

[0053] The present invention also provides the use of the aforementioned polylactic acid composite material in the preparation of 3D printed polylactic acid filaments suitable for fused deposition modeling 3D printing technology.

[0054] The present invention also provides a polylactic acid filament suitable for fused deposition modeling 3D printing technology, which is prepared by the aforementioned method;

[0055] Preferably, the diameter of the filament is 1.70 to 1.80 mm.

[0056] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0057] (1) By using melt blending-in-situ compatibilization technology, PBAT / POE / POE-MAH is introduced into the PLLA matrix to form a chemical bond between the toughening agent, filler and PLLA, thereby achieving the preparation of PLA composite material with high dispersion and high interfacial bonding force. This solves the problems of low toughness and poor temperature resistance of PLLA extrusion filaments for 3D printing, and provides a modified polylactic acid material for 3D printing with the advantages of wrinkle-free and low warpage of printed parts.

[0058] (2) This invention constructs a multi-scale synergistic toughening-reinforcement PLLA composite material system. A ternary synergistic reinforcement system of "nanocellulose skeleton network + elastomer microspheres + reactive interface compatibilizer" is constructed. The three-dimensional network skeleton constructed by nanocellulose improves the rigidity of the matrix, the core-shell structure elastomer microspheres realize energy dissipation, and the reactive compatibilizer containing epoxy groups generates chemical crosslinking points in situ during the melting process. This successfully breaks through the technical bottleneck of "reinforcement makes it brittle, toughening makes it soft" in traditional PLA modification technology, and provides a preparation method for 3D printing polylactic acid modified materials.

[0059] (3) In this invention, POE is innovatively added as a toughening agent while adding PBAT, which fully utilizes the toughening effect of different toughening agents on polylactic acid. The addition of POE can also play a plasticizing role, which can improve the surface gloss of the product and improve the flexibility of 3D printed polylactic acid products.

[0060] (4) The present invention innovatively uses POE-MAH as a compatibilizer and nano silica as a nanofiller, which can not only increase the compatibility between the toughening agent and the polylactic acid matrix, but also improve the melt index and impact strength of the polylactic acid modified material.

[0061] (5) The polylactic acid modified by the present invention has good flexibility and elongation at break, and its heat resistance is also greatly improved.

[0062] (6) The entire process of polylactic acid modification innovatively adopts high-speed powder mixing instead of the secondary extrusion of the twin-screw extruder, which can effectively ensure the uniform dispersion of nano silica and avoid the degradation reaction of polylactic acid due to high temperature.

[0063] (7) The modified polylactic acid of the present invention can be used for 3D printing, which solves the problems of PLA material printing not being smooth, easy to pull, easy to warp, and easy to form wrinkles in the existing technology. The whole printing process is smooth and the printed product has a smooth surface, beautiful appearance, uniformity, stable size and no warping.

[0064] In summary, this invention constructs a ternary synergistic reinforcement system consisting of a "nanocellulose framework network + elastomer microspheres + reactive interfacial compatibilizer." The three-dimensional network framework built with nanocellulose enhances matrix rigidity, while the core-shell structured elastomer microspheres dissipate energy. By optimizing the proportions of PLLA to PDLA, PBAT to ADR, and POE to POE-MAH, nanoparticle-coated elastomer microspheres are effectively constructed, effectively promoting interfacial compatibility and improving nanoparticle dispersion, thus significantly improving the mechanical properties and impact strength of polylactic acid (PLA). Furthermore, by controlling the proportion of nano-silica, the mechanical properties and melt flowability of the PLA composite material are further optimized, while ensuring its low cost and practicality. More significantly, based on the addition of a certain proportion of PLLA and PDLA, a certain proportion of crosslinking agent is introduced, resulting in a higher content of stereocomposite crystals even with low PLLA content. This allows the PLLA-modified composite material to maintain high mechanical properties while exhibiting a high crystallization rate, thereby improving the composite material's heat resistance. Through the synergistic effect of ADR, ATBC, and PBAT, the toughness of existing 3D printed polylactic acid filaments is improved while effectively overcoming the defects of easy breakage, poor interlayer force, and low printing flow rate. The method is simple to operate, reduces production costs, and is easy to industrialize. The preparation method described in this invention is simple, and the toughened modified polylactic acid 3D printing filaments obtained have good overall performance.

[0065] The polylactic acid composite material provided by this invention not only provides excellent mechanical properties and stable printing results in fused deposition modeling technology, but also meets the requirements for use in high-temperature environments, greatly expanding the application range of 3D printing materials and providing strong support for the further development of 3D printing technology.

[0066] Obviously, based on the above description of the present invention, and according to common technical knowledge and conventional methods in the field, various other modifications, substitutions or alterations can be made without departing from the basic technical concept of the present invention.

[0067] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following embodiments. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Attached Figure Description

[0068] Figure 1 The image shows the results of printing a spherical pendulum using the polylactic acid filament material prepared in Example 1.

[0069] Figure 2 The image shows the results of printing a spherical pendulum using polylactic acid filaments prepared in Example 2.

[0070] Figure 3 The image shows the results of printing a spherical pendulum using the polylactic acid filament material prepared in Example 5.

[0071] Figure 4 The image shows the results of microneedle array printing of polylactic acid filaments prepared for Comparative Example 1. Detailed Implementation

[0072] Unless otherwise stated, all raw materials and equipment used in this invention are known products, obtained by purchasing commercially available products. The main raw materials involved in this invention are as follows:

[0073] Poly(L-lactic acid) (PLLA, Natureworks, 4032D), poly(D-lactic acid) (PDLA, Total, D70), polybutylene terephthalate (PBAT, BASF, C1200), polyolefin elastomer (POE, Dow Chemical, 8401), POE-MAH (POE grafted with maleic anhydride, Mitsui Chemicals, MH5020C), tributyl acetylacetonate (ATBC, Aladdin), BASF chain extender ADR (ADR4380), dicumyl peroxide (DCP, Aladdin), nano silica (800 mesh, Aladdin), cellulose nanocrystals (Xi'an Qiyue Biotechnology Co., Ltd.).

[0074] Example 1: Preparation of high-strength, heat-resistant polylactic acid filaments for 3D printing

[0075] In the preparation of polylactic acid filament in this embodiment, the raw materials are as follows by weight: PLLA 85 parts by weight, PDLA 15 parts by weight, crosslinking agent DCP 0.2 parts by weight, PBAT 5 parts by weight, nano silica 3 parts by weight, chain extender ADR 3 parts by weight, POE 5 parts by weight, ATBC 2 parts by weight, POE-MAH 3 parts by weight, and cellulose nanocrystals 10 parts by weight.

[0076] The preparation method of the high-strength, heat-resistant polylactic acid filament for 3D printing in this embodiment is as follows:

[0077] S1. Place PLLA, PBAT, POE, POE-MAH and nano silica in a vacuum oven and dry at 80℃ for 12 hours.

[0078] S2. Mix the dried PLLA, PDLA, PBAT, POE, POE-MAH, crosslinking agent DCP, ADR and ATBC in a high-speed mixer. Add nano silica during the mixing process and stir continuously until uniform. The stirring speed is 400 rpm and the stirring time is 10 min to ensure uniform mixing.

[0079] S3. The above-mentioned dried mixture and cellulose nanocrystals are placed in a desktop conical twin-screw extruder for co-extrusion. During extrusion, the mixture passes through a die with a circular die to obtain filaments. The filaments are cooled to produce polylactic acid filaments for FDM 3D printing.

[0080] In the desktop conical twin-screw extruder, the screw speed is 30 rpm. When feeding, the screw speed starts from 5 rpm and gradually increases to the maximum speed of 30 rpm. The temperature setting of the twin-screw extruder is divided into three zones from the feed port to the extruder head, which are set as follows: extruder feed port temperature 160℃, extruder middle zone temperature 185℃, and extruder head temperature 190℃.

[0081] The diameter of the extruded polylactic acid filaments is controlled at 1.70-1.75 mm.

[0082] The test sample (polylactic acid filament prepared in this embodiment) was printed using a Tuozhu 3D printer (P1S model). The printing temperature was 220°C, the base plate temperature was 65°C, the fill rate was 100%, and the rest were the default parameters of the equipment.

[0083] Example 2: Preparation of high-strength, heat-resistant polylactic acid filaments for 3D printing

[0084] In the preparation process of polylactic acid filament in this embodiment, the raw materials are as follows by weight: 70 parts by weight of PLLA in S5, 30 parts by weight of PLLA and PDLA in S2 (the mass ratio of PLLA to PDLA is 1:1, that is, 15 parts by weight of PLLA and 15 parts by weight of PDLA), 0.2 parts by weight of crosslinking agent DCP, 5 parts by weight of PBAT, 3 parts by weight of nano-silica, 3 parts by weight of chain extender ADR, 5 parts by weight of POE, 2 parts by weight of ATBC, 3 parts by weight of POE-MAH, and 10 parts by weight of cellulose nanocrystals.

[0085] The preparation method of the high-strength, heat-resistant polylactic acid filament for 3D printing in this embodiment is as follows:

[0086] S1. Place PLLA, PBAT, POE, POE-MAH and nano silica in a vacuum oven and dry at 80℃ for 12 hours.

[0087] S2. The dried PLLA, PDLA and crosslinking agent DCP are co-extruded in a desktop conical twin-screw extruder to prepare a PLLA / PDLA composite. The composite is then dried in a vacuum oven at 80°C to constant weight to obtain a mixture.

[0088] S3. Soak the dried mixture of S2, PBAT, POE, and POE-MAH in liquid nitrogen for 30 minutes, mix them, and then pulverize them into powder at high speed. The particle size of the mixed powder is 300 mesh.

[0089] S4. Then, the mixed powder obtained in S3 is mixed with ADR and ATBC in a high-speed mixer. Nano-silica is added during the mixing process, and the mixture is stirred continuously until it is uniform. The stirring speed is 400 rpm and the stirring time is 10 min to ensure uniform mixing and obtain elastomer microspheres.

[0090] S5. Dry PLLA, cellulose nanocrystals and elastomer microspheres are placed in a desktop conical twin-screw extruder for co-extrusion. During extrusion, the material passes through a die with a circular nozzle to obtain filaments. The filaments are then cooled to produce polylactic acid filaments for FDM 3D printing.

[0091] In the desktop conical twin-screw extruder, the screw speed is 30 rpm. When feeding, the screw speed starts from 5 rpm and gradually increases to the maximum speed of 30 rpm. The temperature setting of the twin-screw extruder is divided into three zones from the feed port to the extruder head, which are set as follows: extruder feed port temperature 160℃, extruder middle zone temperature 185℃, and extruder head temperature 190℃.

[0092] The diameter of the extruded polylactic acid filaments is controlled at 1.70-1.75 mm.

[0093] The test sample (polylactic acid filament prepared in this embodiment) was printed using a Tuozhu 3D printer (P1S model). The printing temperature was 220°C, the base plate temperature was 65°C, the fill rate was 100%, and the rest were the default parameters of the equipment.

[0094] Example 3: Preparation of high-strength, heat-resistant polylactic acid filaments for 3D printing

[0095] In the preparation process of polylactic acid filament in this embodiment, the raw materials are as follows by weight: 70 parts by weight of PLLA in S5, 30 parts by weight of PLLA and PDLA in S2 (the mass ratio of PLLA and PDLA is 1:1, that is, 15 parts by weight of PLLA and 15 parts by weight of PDLA), 5 parts by weight of PBAT, 3 parts by weight of nano-silica, 3 parts by weight of chain extender ADR, 5 parts by weight of POE, 2 parts by weight of ATBC, 3 parts by weight of POE-MAH, and 10 parts by weight of cellulose nanocrystals.

[0096] The preparation method of the high-strength, heat-resistant polylactic acid filament for 3D printing in this embodiment is as follows:

[0097] S1. Place PLLA, PBAT, POE, POE-MAH and nano silica in a vacuum oven and dry at 80℃ for 12 hours.

[0098] S2. The dried PLLA and PDLA were co-extruded in a desktop conical twin-screw extruder to prepare a PLLA / PDLA composite; the composite was then dried in a vacuum oven at 80°C to constant weight to obtain a mixture.

[0099] S3. Soak the dried mixture of S2, PBAT, POE, and POE-MAH in liquid nitrogen for 30 minutes, mix them, and then pulverize them into powder at high speed. The particle size of the mixed powder is 300 mesh.

[0100] S4. Then, the mixed powder obtained in S3 is mixed with ADR and ATBC in a high-speed mixer. Nano-silica is added during the mixing process, and the mixture is stirred continuously until it is uniform. The stirring speed is 400 rpm and the stirring time is 10 min to ensure uniform mixing and obtain elastomer microspheres.

[0101] S5. Dry PLLA, cellulose nanocrystals and elastomer microspheres are placed in a desktop conical twin-screw extruder for co-extrusion. During extrusion, the material passes through a die with a circular nozzle to obtain filaments. The filaments are then cooled to produce polylactic acid filaments for FDM 3D printing.

[0102] In the desktop conical twin-screw extruder, the screw speed is 30 rpm. When feeding, the screw speed starts from 5 rpm and gradually increases to the maximum speed of 30 rpm. The temperature setting of the twin-screw extruder is divided into three zones from the feed port to the extruder head, which are set as follows: extruder feed port temperature 160℃, extruder middle zone temperature 185℃, and extruder head temperature 190℃.

[0103] The diameter of the extruded polylactic acid filaments is controlled at 1.70-1.75 mm.

[0104] The test sample (polylactic acid filament prepared in this embodiment) was printed using a Tuozhu 3D printer (P1S model). The printing temperature was 220°C, the base plate temperature was 65°C, the fill rate was 100%, and the rest were the default parameters of the equipment.

[0105] Example 4: Preparation of high-strength, heat-resistant polylactic acid filaments for 3D printing

[0106] In the preparation process of polylactic acid filament in this embodiment, the raw materials are as follows by weight: 70 parts by weight of PLLA in S5, 30 parts by weight of PLLA and PDLA in S2 (the mass ratio of PLLA to PDLA is 1:1, that is, 15 parts by weight of PLLA and 15 parts by weight of PDLA), 0.2 parts by weight of crosslinking agent DCP, 5 parts by weight of PBAT, 3 parts by weight of nano-silica, 3 parts by weight of chain extender ADR, 5 parts by weight of POE, 3 parts by weight of POE-MAH, and 10 parts by weight of cellulose nanocrystals.

[0107] The preparation method of the high-strength, heat-resistant polylactic acid filament for 3D printing in this embodiment is as follows:

[0108] S1. Place PLLA, PBAT, POE, POE-MAH and nano silica in a vacuum oven and dry at 80℃ for 12 hours.

[0109] S2. The dried PLLA, PDLA and crosslinking agent DCP were co-extruded in a desktop conical twin-screw extruder to prepare a PLLA / PDLA composite; the composite was then dried in a vacuum oven at 80°C to constant weight to obtain a mixture.

[0110] S3. Soak the dried mixture of S2, PBAT, POE, and POE-MAH in liquid nitrogen for 30 minutes, mix them, and then pulverize them into powder at high speed. The particle size of the mixed powder is 300 mesh.

[0111] S4. Then, the mixed powder obtained in S3 is mixed with ADR in a high-speed mixer. Nano silica is added during the mixing process, and the mixture is stirred continuously until it is uniform. The stirring speed is 400 rpm and the stirring time is 10 min to ensure uniform mixing and obtain elastomer microspheres.

[0112] S5. Dry PLLA, cellulose nanocrystals and elastomer microspheres are placed in a desktop conical twin-screw extruder for co-extrusion. During extrusion, the material passes through a die with a circular nozzle to obtain filaments. The filaments are then cooled to produce polylactic acid filaments for FDM 3D printing.

[0113] In the desktop conical twin-screw extruder, the screw speed is 30 rpm. When feeding, the screw speed starts from 5 rpm and gradually increases to the maximum speed of 30 rpm. The temperature setting of the twin-screw extruder is divided into three zones from the feed port to the extruder head, which are set as follows: extruder feed port temperature 160℃, extruder middle zone temperature 185℃, and extruder head temperature 190℃.

[0114] The diameter of the extruded polylactic acid filaments is controlled at 1.70-1.75 mm.

[0115] The test sample (polylactic acid filament prepared in this embodiment) was printed using a Tuozhu 3D printer (P1S model). The printing temperature was 220°C, the base plate temperature was 65°C, the fill rate was 100%, and the rest were the default parameters of the equipment.

[0116] Example 5: Preparation of high-strength, heat-resistant polylactic acid filaments for 3D printing

[0117] In the preparation process of polylactic acid filament in this embodiment, the raw materials are as follows by weight: 70 parts by weight of PLLA in S5, 30 parts by weight of PLLA and PDLA in S2 (the mass ratio of PLLA to PDLA is 1:1, that is, 15 parts by weight of PLLA and 15 parts by weight of PDLA), 0.2 parts by weight of crosslinking agent DCP, 5 parts by weight of PBAT, 3 parts by weight of nano silica, 3 parts by weight of chain extender ADR, 5 parts by weight of POE, 2 parts by weight of ATBC, and 3 parts by weight of POE-MAH.

[0118] The preparation method of the high-strength, heat-resistant polylactic acid filament for 3D printing in this embodiment is as follows:

[0119] S1. Place PLLA, PBAT, POE, POE-MAH and nano silica in a vacuum oven and dry at 80℃ for 12 hours.

[0120] S2. The dried PLLA, PDLA and crosslinking agent DCP were co-extruded in a desktop conical twin-screw extruder to prepare a PLLA / PDLA composite; the composite was then dried in a vacuum oven at 80°C to constant weight to obtain a mixture.

[0121] S3. Soak the dried mixture of S2, PBAT, POE, and POE-MAH in liquid nitrogen for 30 minutes, mix them, and then pulverize them into powder at high speed. The particle size of the mixed powder is 300 mesh.

[0122] S4. Then, the mixed powder obtained in S3 is mixed with ADR and ATBC in a high-speed mixer. Nano-silica is added during the mixing process, and the mixture is stirred continuously until it is uniform. The stirring speed is 400 rpm and the stirring time is 10 min to ensure uniform mixing and obtain elastomer microspheres.

[0123] S5. The dried PLLA and elastomer microspheres are placed in a desktop conical twin-screw extruder for co-extrusion. During extrusion, the material passes through a die with a circular die to obtain filaments. The filaments are then cooled to produce polylactic acid filaments for FDM 3D printing.

[0124] In the desktop conical twin-screw extruder, the screw speed is 30 rpm. When feeding, the screw speed starts from 5 rpm and gradually increases to the maximum speed of 30 rpm. The temperature setting of the twin-screw extruder is divided into three zones from the feed port to the extruder head, which are set as follows: extruder feed port temperature 160℃, extruder middle zone temperature 185℃, and extruder head temperature 190℃.

[0125] The diameter of the extruded polylactic acid filaments is controlled at 1.70-1.75 mm.

[0126] The test sample (polylactic acid filament prepared in this embodiment) was printed using a Tuozhu 3D printer (P1S model). The printing temperature was 220°C, the base plate temperature was 65°C, the fill rate was 100%, and the rest were the default parameters of the equipment.

[0127] Spherical pendulums were printed using the 3D-printed polylactic acid (PLA) filaments prepared in Examples 1-5 (to verify whether the strength and toughness of the PLA filaments met the basic requirements). The spheres were all printed completely and smoothly, with smooth material output, no clogging or warping, and exhibited good flowability in microneedle array printing without filament pulling. This indicates that the 3D-printed PLA filaments prepared in Examples 1-5 possess good flowability, toughness, and strength. The results of spherical pendulums printed using the 3D-printed PLA filaments from some examples are shown below. Figures 1-3 As shown.

[0128] Comparative Example 1: Preparation of other polylactic acid filaments for 3D printing

[0129] The preparation method of the polylactic acid filament used for 3D printing in this comparative example is the same as that in Example 2, except that the weight ratio of the raw materials is different.

[0130] In this comparative example, the raw materials are as follows by weight: 80 parts by weight of PLLA in S5, 20 parts by weight of PLLA and PDLA in S2 (the mass ratio of PLLA to PDLA is 1:1, i.e., 10 parts by weight of PLLA and 10 parts by weight of PDLA), 0.2 parts by weight of crosslinking agent DCP, 5 parts by weight of PBAT, 3 parts by weight of nano-silica, 3 parts by weight of chain extender ADR, 5 parts by weight of POE, 2 parts by weight of ATBC, 3 parts by weight of POE-MAH, and 10 parts by weight of cellulose nanocrystals.

[0131] The printing results of the 3D printed polylactic acid filaments prepared by this comparative method: the spherical pendulum can be printed completely, but a small amount of granular aggregates appeared on the surface of the sphere. The material flow was smooth, without clogging or warping. In addition, a large amount of filament pulling occurred in the microneedle array printing. Figure 4 The results indicate that the 3D printing effect of the polylactic acid filament prepared in this comparative example is poor.

[0132] Comparative Example 2: Preparation of other polylactic acid filaments for 3D printing

[0133] The preparation method of the polylactic acid filament used for 3D printing in this comparative example is the same as that in Example 2, except that the weight ratio of the raw materials is different.

[0134] In this comparative example, the raw materials are as follows by weight: 70 parts by weight of PLLA in S5, 30 parts by weight of PLLA and PDLA in S2 (the mass ratio of PLLA to PDLA is 1:1, i.e., 15 parts by weight of PLLA and 15 parts by weight of PDLA), 0.2 parts by weight of crosslinking agent DCP, 5 parts by weight of PBAT, 3 parts by weight of nano-silica, 3 parts by weight of chain extender ADR, 5 parts by weight of POE, 4 parts by weight of ATBC, 3 parts by weight of POE-MAH, and 20 parts by weight of cellulose nanocrystals.

[0135] The 3D printed polylactic acid filament pendulum prepared using this comparative method resulted in the following: the sphere could not be printed completely, and the material output was not smooth, indicating that the printing effect of the 3D printed filament was poor.

[0136] Comparative Example 3: Preparation of other polylactic acid filaments for 3D printing

[0137] The preparation method of the polylactic acid filament used for 3D printing in this comparative example is the same as that in Example 2, except that the weight ratio of the raw materials is different.

[0138] In this comparative example, the raw materials are as follows by weight: 70 parts by weight of PLLA in S5, 30 parts by weight of PLLA and PDLA in S2 (the mass ratio of PLLA to PDLA is 1:1, that is, 15 parts by weight of PLLA and 15 parts by weight of PDLA), 0.4 parts by weight of crosslinking agent DCP, 5 parts by weight of PBAT, 3 parts by weight of nano silica, 3 parts by weight of chain extender ADR, 5 parts by weight of POE and 2 parts by weight of ATBC.

[0139] The specific steps and process parameters of the preparation method are the same as in Example 2, except that the raw materials POE-MAH and cellulose nanocrystals are not added.

[0140] The 3D printed polylactic acid filament pendulum prepared using this comparative method was able to print the sphere completely, but a small amount of granular aggregates appeared on the surface of the sphere. The material flow was smooth, without clogging or warping. A small amount of filament pulling occurred during the microneedle array printing, indicating that the printing effect of the 3D printed filament was generally poor.

[0141] The following specific experimental examples demonstrate the beneficial effects of the present invention.

[0142] Experimental Example 1: Performance Characterization of Products Printed with Polylactic Acid Filament

[0143] The polylactic acid filaments for 3D printing prepared in Examples 1-5 and Comparative Examples 1-3 were used to print products using the 3D printing method described in the examples. The performance of the obtained products was verified. Tensile properties were tested according to the national standard GB / T 1040.1-2018. Heat distortion temperature testing was performed according to the national standard GB / T1634.2-2004. The stereocomplex crystal structure was tested using DSC. The results are shown in Table 1 below:

[0144] Table 1. Performance of 3D printed products obtained in Examples 1-5 and Comparative Examples 1-3

[0145]

[0146] The results from Examples 1-5 and Comparative Examples 1-3 show that the materials 3D printed using the polylactic acid filaments of this invention exhibit improved tensile strength and heat resistance, with a particularly significant improvement in heat resistance. This greatly enhances the practicality and applicability of PLLA consumables. This demonstrates that the synergistic effect of the ternary structure of "nanocellulose framework network + elastomer microspheres + reactive interface compatibilizer" can significantly improve the interfacial compatibility of the composite material, thereby increasing its strength and heat distortion temperature. By adjusting the PLLA / PDLA ratio and optimizing the ratio of ATBC and cellulose nanocrystals, a synergistic effect can be achieved, significantly improving the strength and heat distortion temperature of the 3D printed filaments within a specific ratio range, enhancing processing performance, and indicating broad application prospects.

Claims

1. A polylactic acid composite material suitable for 3D printing, characterized in that: It is prepared from the following raw materials in the following weight ratio: 80-100 parts by weight of poly(L-)polylactic acid, 1-20 parts by weight of poly(D-)polylactic acid, 5-15 parts by weight of toughening agent, 1-5 parts by weight of chain extender, 0-5 parts by weight of plasticizer, 0-0.5 parts by weight of crosslinking agent, 0-5 parts by weight of compatibilizer, 1-5 parts by weight of nanofiller, and 0-20 parts by weight of cellulose nanocrystals.

2. The polylactic acid composite material according to claim 1, characterized in that: It is prepared from the following raw materials in the following weight ratio: 85-95 parts by weight of poly(L-)polylactic acid, 15 parts by weight of poly(D-)polylactic acid, 10 parts by weight of toughening agent, 3 parts by weight of chain extender, 0-4 parts by weight of plasticizer, 0-0.4 parts by weight of crosslinking agent, 0-3 parts by weight of compatibilizer, 3 parts by weight of nanofiller, and 0-20 parts by weight of cellulose nanocrystals.

3. The polylactic acid composite material according to claim 2, characterized in that: It is prepared from the following raw materials in the following weight ratio: 85 parts by weight of poly(L-)polylactic acid, 15 parts by weight of poly(D-)polylactic acid, 10 parts by weight of toughening agent, 3 parts by weight of chain extender, 0-2 parts by weight of plasticizer, 0-0.2 parts by weight of crosslinking agent, 3 parts by weight of compatibilizer, 3 parts by weight of nanofiller, and 0-10 parts by weight of cellulose nanocrystals.

4. The polylactic acid composite material according to any one of claims 1 to 3, characterized in that: The toughening agent is selected from one or more of thermoplastic elastomers, thermoplastic polyurethane elastomers, polyolefin elastomers, polycaprolactone, ethylene-vinyl acetate copolymer, and polybutylene terephthalate; And / or, the chain extender is selected from BASF ADR chain extenders; And / or, the plasticizer is selected from acetylated tributyl citrate, triethyl citrate, or tributyl citrate; And / or, the crosslinking agent is selected from benzoyl peroxide or dicumyl peroxide; And / or, the compatibilizer is selected from POE-grafted maleic anhydride; And / or, the nanofiller is selected from one or more of nano silica, nano calcium carbonate, or nano montmorillonite.

5. The polylactic acid composite material according to claim 4, characterized in that: The toughening agent is composed of polybutylene terephthalate and polyolefin elastomer, with a mass ratio of polybutylene terephthalate to polyolefin elastomer of 1:

1. And / or, the plasticizer is selected from tributyl acetylcitrate; And / or, the crosslinking agent is selected from dicumyl peroxide; And / or, the nanofiller is selected from nano-silica.

6. The polylactic acid composite material according to claim 5, characterized in that: It is prepared from the following raw materials in the following weight ratio: 85 parts by weight of poly(L-lactic acid), 15 parts by weight of poly(D-lactic acid), 5 parts by weight of polybutylene terephthalate-adipate, 5 parts by weight of polyolefin elastomer, 3 parts by weight of BASF ADR chain extender, 2 parts by weight of acetylsalicylic acid tributyl ester, 0.2 parts by weight of dicumyl peroxide, 3 parts by weight of POE-MAH, 3 parts by weight of nano-silica, and 10 parts by weight of cellulose nanocrystals.

7. The method for preparing the polylactic acid composite material according to any one of claims 1 to 6, characterized in that: It includes the following steps: (1) Weigh each raw material according to any one of claims 1 to 6; (2) Mix poly(L-)-polylactic acid, poly(D-)-polylactic acid, toughening agent, compatibilizer, nanofiller, crosslinking agent, chain extender and plasticizer evenly to obtain a mixture; (3) The mixture obtained in step (2) and cellulose nanocrystals are co-extruded and cooled to obtain polylactic acid composite material; Preferably, in step (2), the mixing is carried out at a speed of 100 to 1000 rpm for a duration of 1 to 60 min. And / or, in step (3), a twin-screw extruder is used for the blending extrusion, with a screw speed of 5 to 30 rpm, an extruder feed port temperature of 140 to 160°C, an extruder middle zone temperature of 170 to 185°C, and an extruder die head temperature of 190 to 200°C.

8. The method for preparing the polylactic acid composite material according to any one of claims 1 to 6, characterized in that: It includes the following steps: (a) Weigh each raw material according to any one of claims 1 to 6; (b) Poly(L-)-polylactic acid, poly(D-)-polylactic acid and a crosslinking agent in a mass percentage of 15-18% were co-extruded to obtain a PLLA / PDLA composite. (c) The PLLA / PDLA complex, toughening agent and compatibilizer are mixed and then pulverized into powder; (d) Mix the powder, chain extender, plasticizer and nanofiller obtained in step (c) evenly to obtain elastomer microspheres; (e) Poly(L-lactic acid), cellulose nanocrystals, and elastomer microspheres obtained in step (d) are blended and extruded with a remaining mass percentage of 82-85% and cooled to obtain a polylactic acid composite material. Preferably, In step (b), a twin-screw extruder is used for the blending extrusion, with a screw speed of 5 to 30 rpm, an extruder feed port temperature of 140 to 160°C, an extruder middle zone temperature of 170 to 185°C, and an extruder die head temperature of 190 to 200°C. And / or, in step (d), the mixing is carried out by stirring at a speed of 100 to 1000 rpm for a time of 1 to 60 min; And / or, in step (e), a twin-screw extruder is used for the blending extrusion, with a screw speed of 5 to 30 rpm, an extruder feed port temperature of 140 to 160°C, an extruder intermediate zone temperature of 170 to 185°C, and an extruder die head temperature of 190 to 200°C.

9. Use of the polylactic acid composite material according to any one of claims 1 to 6 in the preparation of 3D printed polylactic acid filaments suitable for fused deposition modeling 3D printing technology.

10. A polylactic acid filament suitable for fused deposition modeling (FDM) 3D printing technology, characterized in that: It is prepared using the method described in claim 7 or 8; Preferably, the diameter of the filament is 1.70 to 1.80 mm.

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