A 3D-printed polypropylene material with interlayer bonding interface and its preparation method

Abstract

This invention relates to a 3D printing polypropylene material with interlayer bonding interface and its preparation method, belonging to the field of 3D printing material preparation technology. The 3D printing polypropylene material of this invention has advantages such as high interlayer bonding interface strength and good toughness, and is suitable for solving the technical problems of mechanical anisotropy and poor toughness in existing 3D printed polypropylene parts.

Description

Technical Field

[0001] This invention belongs to the field of 3D printing preparation technology, and relates to a 3D printing polypropylene material with interlayer bonding interface and its preparation method. Background Technology

[0002] Fused deposition modeling (FDM) technology forms polymer filaments by layering polymer melts. This not only overcomes the limitations of traditional processing and molding on shape and structural design but also allows for the control of the microstructure of thermoplastic polymers, providing a promising method for near-net-shape forming, flexible design, and rapid verification of lightweight, high-strength components in the automotive and medical fields. Polypropylene, an important general-purpose plastic, can form self-reinforcing structures such as microfibers, crystalline strands, and orientation under the combined action of the shear and temperature fields of FDM, enabling the rapid manufacture of complex, high-toughness components. It is one of the key materials driving the application of FDM technology in various fields. However, the inherent high cooling rate and complex temperature variations of the FDM process often cause polypropylene to form unpredictable crystalline structures and insufficient molecular chain topological entanglement at the interlayer interfaces, resulting in weak and brittle interlayer interfaces and significant anisotropy in mechanical properties, affecting its assembly accuracy and load-bearing capacity.

[0003] Currently, researchers are proposing various technologies to enhance the interlayer interface properties of polypropylene FDM molded parts, primarily focusing on both process and materials. In terms of process, optimizing printing parameters, in-situ laser preheating, and post-processing can improve interlayer interface strength and toughness by enhancing molecular chain mobility and extending healing time. Regarding materials, chemical and physical methods have been developed to modify printing materials (Patent CN 115785571 A improves interlayer bonding strength by adding low-melting-point polyester polyols to polypropylene resin, utilizing the strong cohesive strength and adhesion of ester groups; Patent CN 111073160 A adds acrylate adhesives to polypropylene, enhancing interlayer bonding strength through the strong polar groups of phenolic hydroxyl groups in dopamine graft copolymers). However, the interlayer bonding strength (9.37 MPa) and toughness of the modified materials are far lower than the bulk strength of the polypropylene material.

[0004] Therefore, it is necessary to study new modification methods, such as constructing chemically bonded network structures at the interlayer interface to enhance the interlayer interface properties of 3D printed parts. Summary of the Invention

[0005] In view of this, one objective of the present invention is to provide a 3D printing polypropylene material with interlayer bonding interface; another objective of the present invention is to provide a method for preparing a 3D printing polypropylene material with interlayer bonding interface.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] 1. A 3D printing polypropylene material for interlayer bonding interfaces, wherein, by weight, the 3D printing polypropylene material comprises 70-90 parts of polypropylene, 10-20 parts of acrylic copolymer, 1-10 parts of modified inorganic filler, and 0.1-1 parts of antioxidant;

[0008] The modified inorganic filler is an inorganic filler containing one or more of thiol groups, epoxy groups, amino groups or hydroxyl groups on its surface, wherein the inorganic filler is any one or two of silica or montmorillonite.

[0009] The antioxidant is any one or more of the following: hindered phenolic antioxidants, phosphorous antioxidants, or alkyl ester antioxidants.

[0010] Preferably, the acrylic copolymer has an acid content of 4-10% and a melt index of 2-15 g / 10 min when tested under test conditions of 190°C / 2.16 kg.

[0011] More preferably, the melt index of the acrylic copolymer tested at 190°C / 2.16 kg is 5-10 g / 10 min.

[0012] More preferably, the acrylic copolymer is any one or more of ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene / ethyl acrylate copolymer, or ethylene vinyl acetate copolymer.

[0013] Preferably, the modified inorganic filler is prepared according to the following method:

[0014] A. Add inorganic filler to a solvent and sonicate to obtain an inorganic filler suspension, wherein the solvent is any one or more of toluene, xylene, ethanol or water;

[0015] B. Under nitrogen protection, the silane organic compound is added dropwise to the inorganic filler suspension and stirred at 100-120°C for 2-24 hours. The silane organic compound is any one or more of aminosilane, methacryloxysilane, epoxysilane, mercaptosilane or long-chain silane, wherein the long-chain silane has a main chain with a number of carbon atoms of not less than 10.

[0016] C. After the reaction is complete, wash with ethanol to remove residual silane organic compounds, and then vacuum dry at 25-120℃ for 2-24 hours to obtain the modified inorganic filler.

[0017] More preferably, the mass ratio of the silane coupling agent to the inorganic filler is 1 to 3:1.

[0018] Preferably, the average particle size of the modified inorganic filler is 50–300 nm.

[0019] Preferably, the antioxidant is a mixture of phenolic antioxidant 1010 and phosphite antioxidant 168 in a 1:1 mass ratio.

[0020] 2. The preparation method of the above-mentioned 3D printing polypropylene material is as follows:

[0021] (1) According to the weight parts, polypropylene, acrylic copolymer, modified inorganic filler and antioxidant are mixed, stirred evenly and then fed into a twin screw extruder. After being melted and mixed evenly, the mixture is extruded, granulated and dried to obtain polypropylene composite granules.

[0022] (2) The polypropylene composite granules are fed into a single screw extruder, melted and extruded into a water bath at 25-50°C, and extruded into fibers to obtain 3D printed polypropylene material with interlayer bonding interface.

[0023] The beneficial effects of this invention are as follows: This invention discloses a 3D printing polypropylene material with a high interlayer bonding interface, comprising, by weight, 70-90 parts polypropylene, 10-20 parts acrylic copolymer, 1-10 parts modified inorganic filler, and 0.1-1 parts antioxidant. The 3D printing polypropylene material of this invention has advantages such as high interlayer bonding interface strength and good toughness, and is suitable for solving the technical problems of low interlayer bonding interface strength and poor toughness in existing 3D printing polypropylene materials.

[0024] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0026] Figure 1 This is a diagram illustrating the formation mechanism of chemical bonds at the interlayer interface of the 3D-printed polypropylene material with a high-layer bonding interface prepared in Example 2.

[0027] Figure 2 The printed part is obtained by 3D printing the polypropylene material with interlayer bonding interface prepared in Example 2. Detailed Implementation

[0028] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0029] Example 1

[0030] A 3D-printed polypropylene composite material with interlayer bonding interfaces is prepared according to the following method:

[0031] (1) Preparation of modified inorganic fillers: A. A) Silica with an average spherical diameter of 300 nm was added to toluene and ultrasonically treated to obtain a silica suspension. B) Under nitrogen protection, epoxy silane coupling agent KH-560 (with a mass ratio of KH-560 to silica of 2:1) was added dropwise to the silica suspension, and the mixture was stirred at 110 °C for 24 h. C) After the reaction was completed, residual KH-560 was removed by washing with ethanol, and the mixture was vacuum dried at 25 °C for 12 h to obtain silica with epoxy groups and an average particle size range of 50–300 nm.

[0032] (2) Mix 80 parts of polypropylene (1100N, Ningmei), 10 parts of ethylene-methacrylic acid copolymer (EMAA, DuPont Nucrel™ 2940), 10 parts of silica with epoxy groups and 0.5 parts of antioxidant (a mixture formed by phenolic antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 1:1), stir evenly, put into a twin-screw extruder to melt and mix evenly, extrude, then granulate and dry to obtain polypropylene composite granules;

[0033] (3) The polypropylene composite granules are fed into a single screw extruder, melted and extruded into a water bath at 40°C, and stretched by a traction machine to form a 3D printed polypropylene material with a diameter of 1.75±0.05mm.

[0034] Example 2

[0035] A 3D-printed polypropylene composite material with interlayer bonding interfaces is prepared according to the following method:

[0036] (1) Preparation of modified inorganic fillers: A. A) The synthesized silica with an average spherical diameter of 300 nm was added to toluene and ultrasonically treated to obtain a silica suspension; B) Under nitrogen protection, a silane organic compound (γ-mercaptopropyltriethoxysilane) was added dropwise to the silica suspension and stirred at 100 °C for 24 h; C) After the reaction was completed, residual γ-mercaptopropyltriethoxysilane was removed by washing with ethanol to obtain silica with thiol groups, and then dried under vacuum at 25 °C for 24 h.

[0037] (2) 80 parts of polypropylene (1100N, Ningmei), 10 parts of ethylene-methacrylic acid copolymer (EMAA, DuPont Nucrel™ 2940), 10 parts of thiol-containing silica and 0.5 parts of antioxidant (a mixture formed by phenol-resistant antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 1:1) were stirred evenly, then put into a twin-screw extruder to melt and mix evenly, and then granulated and dried to obtain polypropylene composite granules;

[0038] (3) The polypropylene composite granules are fed into a single screw extruder, melt-extruded into a water bath at 40°C, and stretched by a traction machine to produce 3D printed polypropylene material with a diameter of 1.75±0.05mm.

[0039] Example 3

[0040] A 3D-printed polypropylene composite material with interlayer bonding interfaces is prepared according to the following method:

[0041] (1) Preparation of modified inorganic filler: A. Add montmorillonite to xylene and sonicate to obtain montmorillonite suspension; B. Under nitrogen protection, add γ-aminopropyltriethoxysilane dropwise to montmorillonite suspension and stir at 100℃ for 24h; C. After the reaction is completed, wash with ethanol to remove residual γ-aminopropyltriethoxysilane to obtain montmorillonite with amino groups, and vacuum dry at 25℃ for 24h.

[0042] (2) After stirring 70 parts of polypropylene (1100N, Ningmei), 20 parts of ethylene-acrylic acid copolymer (EAA), 10 parts of amino-containing montmorillonite and 0.1 parts of antioxidant (a mixture of phenolic antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 1:1) evenly, put them into a twin-screw extruder to melt and mix evenly, and then granulate and dry to obtain polypropylene composite granules;

[0043] (3) The polypropylene composite granules are fed into a single screw extruder, melt-extruded into a water bath at 25°C, and stretched by a traction machine to produce 3D printed polypropylene material with a diameter of 1.75±0.05mm.

[0044] Example 4

[0045] A 3D-printed polypropylene composite material with interlayer bonding interfaces is prepared according to the following method:

[0046] 1) Preparation of modified inorganic fillers: A. ... A) The synthesized silica with an average spherical diameter of 300 nm was added to toluene and ultrasonically treated to obtain a silica suspension; B) Under nitrogen protection, methacryloyloxypropyltris(trimethylsiloxy)silane was added dropwise to the silica suspension and stirred at 120 °C for 2 h; C) After the reaction was completed, residual methacryloyloxypropyltris(trimethylsiloxy)silane was removed by washing with ethanol to obtain silica with acyloxy groups, and then dried under vacuum at 120 °C for 2 h.

[0047] (2) After stirring 80 parts of polypropylene (1100N, Ningmei), 10 parts of ethylene / ethyl acrylate copolymer (EEA), 10 parts of hydroxyl-containing silica and 1.0 part of antioxidant (a mixture of phenolic antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 1:1) evenly, put them into a twin-screw extruder to melt and mix evenly, and then granulate and dry to obtain polypropylene composite granules;

[0048] (3) The polypropylene composite granules are fed into a single screw extruder, melt-extruded into a water bath at 50°C, and stretched by a traction machine to produce 3D printed polypropylene material with a diameter of 1.75±0.05mm.

[0049] Comparative Example 1

[0050] A 3D-printed polypropylene composite material is prepared according to the following method:

[0051] (1) Preparation of modified inorganic fillers: A. A) The synthesized silica with an average sphere diameter of 300 nm was added to xylene and ultrasonically treated to obtain an inorganic filler suspension; B) Under nitrogen protection, dodecyltrimethoxysilane was added dropwise to the silica suspension and stirred at 120 °C for 24 h; C) After the reaction was completed, the residual silane coupling agent was removed by washing with ethanol to obtain silica with long-chain alkyl groups, and then it was vacuum dried at 25 °C for 12 h.

[0052] (2) After mixing 80 parts of polypropylene (1100N, Ningmei), 10 parts of ethylene-methacrylic acid copolymer (EMAA, DuPont Nucrel™ 2940), 10 parts of silica with long-chain alkyl groups and 0.5 parts of antioxidant evenly, the mixture is put into a twin-screw extruder for melting and mixing evenly. Then, the mixture is granulated and dried to obtain polypropylene composite granules.

[0053] (3) The polypropylene composite granules are fed into a single screw extruder, melt-extruded into a water bath at 40°C, and stretched by a traction machine to produce 3D printed polypropylene material with a diameter of 1.75±0.05mm.

[0054] Comparative Example 2

[0055] A 3D-printed polypropylene composite material is prepared according to the following method:

[0056] (1) After mixing 90 parts of polypropylene (1100N, Ningmei), 10 parts of ethylene-methacrylic acid copolymer (EMAA, DuPont Nucrel™ 2940) and 0.5 parts of antioxidant evenly, the mixture is put into a twin-screw extruder for melting and mixing evenly. Then, the mixture is granulated and dried to obtain polypropylene composite granules.

[0057] (3) The polypropylene composite granules are fed into a single screw extruder, melt-extruded into a water bath at 40°C, and stretched by a traction machine to produce 3D printed polypropylene material with a diameter of 1.75±0.05mm.

[0058] Comparative Example 3

[0059] A 3D-printed polypropylene composite material is prepared according to the following method:

[0060] (1) After mixing 100 parts of polypropylene (1100N, Ningmei) and 0.5 parts of antioxidant evenly, they are put into a twin-screw extruder for melting and mixing evenly. Then, they are granulated and dried to obtain polypropylene composite granules.

[0061] (3) The polypropylene composite granules are fed into a single screw extruder, melt-extruded into a water bath at 40°C, and stretched by a traction machine to produce 3D printed polypropylene material with a diameter of 1.75±0.05mm.

[0062] Testing the interface between layers

[0063] Using a self-made FDM printer, the materials prepared in Examples 1-5 and Comparative Examples 1-3 were used to print A-type dumbbell-shaped tensile specimens as required by ISO 527, with the infill path set at 90° so that the filament arrangement direction was perpendicular to the stress loading direction of the tensile specimen. The tensile properties of the specimens were tested using a universal testing machine to obtain the interlaminar bond strength of the filaments. The nozzle temperature was set to 210°C, the substrate temperature to 90°C, and the printing speed to 40 mm / s.

[0064] Figure 1 This is a diagram showing the formation mechanism of chemical bonds at the interlayer interface of the 3D printed polypropylene material with interlayer bonding interface prepared in Example 2, wherein the functional filler is the 3D printed polypropylene material with interlayer bonding interface prepared in Example 2. Figure 2The printed parts were obtained by 3D printing the polypropylene material with interlayer bonding interface prepared in Example 2. The tensile strength of different materials and the interlayer bonding strength of A-type dumbbell-shaped tensile strips printed from different materials were tested, and the results are shown in Table 1.

[0065] Table 1. Tensile strength of different materials and interlaminar bond strength of A-type dumbbell-shaped tensile specimens printed from different materials.

[0066] Example 1 32.7 30.4 Example 2 31.9 28.7 Example 3 25.7 20.1 Example 4 30.8 22.5 Comparative Example 1 30.5 15.1 Comparative Example 2 20.7 14.2 Comparative Example 3 38.6 13.6

[0067] from Figure 1 , Figure 2 As can be seen from Table 1, the present invention prepares a 3D printing polypropylene material with good tensile strength by adding inorganic fillers containing thiol groups, epoxy groups and amino groups on the surface to the polypropylene and ethylene-acrylic acid copolymer, and the 3D printed parts formed by it have good interlayer bonding strength.

[0068] In summary, this invention discloses a 3D printing polypropylene material with a high interlayer bonding interface, comprising, by weight, 70-90 parts polypropylene, 10-20 parts ethylene-acrylic acid copolymer, 1-10 parts modified inorganic filler, and 0.1-1 parts antioxidant. The 3D printing polypropylene material of this invention has advantages such as high interlayer bonding interface strength and good toughness, and is suitable for solving the technical problem of mechanical anisotropy in existing 3D printing polypropylene.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A 3D-printed polypropylene material for interlayer bonding interfaces, characterized in that, The raw material composition of the 3D printing polypropylene material, by weight, is: 70-90 parts polypropylene, 10-20 parts acrylic copolymer, 1-10 parts modified inorganic filler, and 0.1-1 parts antioxidant. The modified inorganic filler is an inorganic filler containing one or more of thiol groups, epoxy groups, amino groups or hydroxyl groups on its surface, wherein the inorganic filler is any one or two of silica or montmorillonite. The antioxidant is any one or more of hindered phenolic antioxidants, phosphorous antioxidants, or alkyl ester antioxidants; The diameter of the 3D printed polypropylene material is 1.75±0.05mm.

2. The 3D printing polypropylene material according to claim 1, characterized in that, The acrylic copolymer has an acid content of 4-10% and a melt index of 2-15 g / 10min when tested at 190℃ / 2.16Kg.

3. The 3D printing polypropylene material according to claim 2, characterized in that, The melt flow index of the acrylic copolymer tested at 190℃ / 2.16Kg was 5~10 g / 10min.

4. The 3D printing polypropylene material according to claim 2, characterized in that, The acrylic copolymer is any one or more of ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, or ethylene / ethyl acrylate copolymer.

5. The 3D printing polypropylene material according to claim 1, characterized in that, The modified inorganic filler is prepared according to the following method: A. An inorganic filler is added to a solvent and ultrasonically treated to obtain an inorganic filler suspension, wherein the solvent is any one or more of toluene, xylene, ethanol or water; B. Under nitrogen protection, the silane organic compound is added dropwise to the inorganic filler suspension and stirred at 100~120℃ for 2~24h. The silane organic compound is any one or more of aminosilane, epoxysilane or mercaptosilane. C. After the reaction is complete, wash with ethanol to remove residual silane organic compounds, and then vacuum dry at 25~120℃ for 2~24h to obtain the modified inorganic filler.

6. The 3D printing polypropylene material according to claim 5, characterized in that, The mass ratio of the silane organic compound to the inorganic filler is 1:1 to 3:

1.

7. The 3D printing polypropylene material according to claim 1, characterized in that, The average particle size of the modified inorganic filler is 50~300 nm.

8. The 3D printing polypropylene material according to claim 1, characterized in that, The antioxidant is a mixture of phenol-resistant antioxidant 1010 and phosphite antioxidant 168 in a 1:1 mass ratio.

9. A method for preparing the 3D printing polypropylene material according to any one of claims 1 to 8, characterized in that, The specific preparation method is as follows: (1) According to the weight parts, polypropylene, acrylic copolymer, modified inorganic filler and antioxidant are mixed, stirred evenly and then fed into a twin screw extruder. After being melted and mixed evenly, the mixture is extruded, granulated and dried to obtain polypropylene composite granules. (2) The polypropylene composite granules are fed into a single screw extruder, melted and extruded into a water bath at 25~50℃, and extruded into fibers to obtain 3D printed polypropylene material with interlayer bonding interface.

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