High-strength and high-toughness polypropylene 3D printing wire rod and preparation method thereof

Abstract

The invention discloses a high-strength and high-toughness polypropylene 3D printing wire and a preparation method thereof.The preparation method comprises the steps that thermoplastic elastomer TPU coated glass fibers, a compatilizer, tackifying resin, an antioxidant and other components are introduced into a polypropylene matrix, mixed extrusion is conducted through a double-screw extruder, and then the filamentous printing wire is extruded through a single-screw extruder. The raw materials are easy to obtain, the preparation process is simple and efficient, the cost is low, and the prepared polypropylene wire has high strength and high toughness, can be widely and stably applied to the field of 3D printing, and has wide application prospects in the aspect of high-strength and high-toughness structural parts.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and in particular relates to a high-performance 3D printing wire based on polypropylene and a preparation method thereof. Background Art

[0002] Polypropylene (PP) materials have been widely used in many fields due to their diverse raw material sources, mature preparation processes, low cost, high melting point and softening point, low density, and excellent heat resistance, water resistance, and chemical stability. In 3D printing technologies such as FDM, the application of polypropylene has also attracted increasing attention. However, PP has a large molding shrinkage rate, and the products are prone to warping and difficult to mold during the printing process. In response to these problems, a variety of modification methods have been developed to optimize its performance. Patent CN 103739954 B uses toughening agents and nucleating agents to regulate the crystallization properties of PP molding and reduce the molding shrinkage rate to achieve the purpose of FDM printing. CN108641197 B uses copolymer random polypropylene with a small degree of crystallinity as a raw material, and prepares polypropylene wire suitable for 3D printing by compounding with fillers and other additives. CN 110437538 B uses a method of filling with inorganic fillers such as talcum powder to reduce the molding shrinkage of PP, and cooperates with toughening agents to prepare 3D printing polypropylene materials. In addition, there are other patents (CN109608762 B, CN 116218123 A and CN 110628130 B, etc.) that use the above method to jointly develop low-shrinkage polypropylene materials suitable for 3D printing.

[0003] However, there are still some problems that need to be improved in the above methods. First, although the selection of low-crystalline polypropylene such as random copolymer PP or the method of nucleating agent control can reduce the molding shrinkage and improve the 3D printing performance, some of its mechanical properties (tensile strength and elastic modulus, etc.) are significantly reduced, resulting in low mechanical properties of some 3D printed products. Second, the use of inorganic fillers such as talcum powder can effectively reduce the molding shrinkage, but to meet certain 3D molding requirements, the amount of addition is large, and a large amount of addition often reduces some properties of polypropylene (such as impact strength and tensile strength, etc.), making the 3D printed products brittle. Therefore, how to greatly improve the performance of PP on the basis of ensuring 3D printing molding and molding accuracy is of great significance to its application.

[0004] Glass fiber is a common and effective polymer filler that can effectively and significantly improve the mechanical properties of molecular materials. Many patents have used glass fiber to prepare high-performance polypropylene composites (CN 114249940 A, CN113444314 B and CN109337198 B, etc.). For 3D printing, since long fibers require specific printing equipment (such as CN114147958 B), general 3D printing equipment can only use short-cut glass fiber reinforcement. Patents CN110628130 B, CN 114524988 B and CN 110229422 A, etc., composite glass fiber with polypropylene to prepare low-shrinkage and high-strength 3D printed polypropylene composites. However, since glass fiber is also an inorganic filler, its large addition will also significantly reduce the impact strength of polypropylene. Therefore, on the basis of 3D printing performance and high tensile strength, it is also important to maintain or improve the toughness of polypropylene. Summary of the invention

[0005] Based on the problems existing in the current application of glass fiber in 3D printing polymer materials. The present invention provides a high-strength and toughness polypropylene wire for 3D printing. The component raw materials of the present invention are easy to obtain, the preparation process is simple and efficient, and the cost is low. The prepared 3D printing polypropylene wire has excellent properties such as high strength, high toughness, and high molding accuracy. It can be widely and stably used in the field of 3D printing, and has strong practicality and wide applicability.

[0006] To achieve the above object, the present invention adopts the following technical solution: A high-strength and tough polypropylene wire for 3D printing, wherein the raw materials used include, by weight: 100 parts of polypropylene, 4-10 parts of a compatibilizer, 30-90 parts of thermoplastic elastomer TPU coated glass fiber, 2-10 parts of a tackifying resin, and 0.05-0.3 parts of an antioxidant.

[0007] Furthermore, the polypropylene is selected from one or both of syndiotactic polypropylene (5-25 g / 10 min, melt flow rate test conditions: 230°C, 2.16 kg; melting temperature 150-190°C) and random polypropylene (20-40 g / 10 min, melt flow rate test conditions: 230°C, 2.16 kg; melting temperature 150-190°C).

[0008] Furthermore, the compatibilizer is a maleic anhydride grafted product, specifically including one or two of maleic anhydride grafted polypropylene and maleic anhydride grafted thermoplastic elastomer TPU.

[0009] Furthermore, the tackifying resin is one or more of terpene resin, hydrogenated rosin and petroleum resin.

[0010] Furthermore, the antioxidant is one or more of a hindered amine antioxidant, a hindered phenol antioxidant, a phosphite antioxidant, and a polymer antioxidant.

[0011] Furthermore, the preparation steps of the thermoplastic elastomer TPU coated glass fiber are as follows: 1) Add glass fiber to 1 mol / L NaOH aqueous solution, stir at room temperature for 2-6 h, then take out and dry; 2) Add the treated glass fiber in step 1) into a mixed solution containing polyester polyol, 1,4-butanediol (BDO), an organic tin catalyst and cyclohexanone, and stir evenly; 3) Add pure 4,4'-diphenylmethane diisocyanate (MDI) to the mixed solution in step 2), stir at high speed, protect with nitrogen and heat to 100 °C, and react for 2 to 6 hours; 4) The solution obtained in step 3) is diluted with cyclohexanone and then filtered. The filtered glass fiber is placed in a vacuum oven at 125° C. (vacuum degree is -90 KPa) and aged for 4 to 8 hours to prepare a thermoplastic elastomer TPU coated glass fiber.

[0012] Wherein, the glass fiber has a mesh size of 50-300; the mass ratio of the glass fiber, polyester polyol, BDO, organotin catalyst and MDI is 100: (30-120): (10-40): (0.3-0.5): (30-90); the mass ratio of cyclohexanone to glass fiber in step 2) is (0.5-1.5): 1; the mass ratio of cyclohexanone to glass fiber in step 4) is (1-3): 1; The preparation of the high-strength and toughness polypropylene wire for 3D printing comprises the following steps: S1, mixing polypropylene, a compatibilizer, a tackifying resin and an antioxidant in proportion to obtain a mixture; S2, feeding the above mixture through the main feeding port of the twin-screw extruder, feeding the thermoplastic elastomer TPU coated glass fiber from the side feeding port, extruding, cooling and then pelletizing with a pelletizer to obtain a granular modified polypropylene composite material; S3. Extrude the obtained granular modified polypropylene composite material through a single screw extruder to obtain filamentous 3D printing polypropylene consumables, which are then wound into bundles and bagged.

[0013] The use of thermoplastic elastomer TPU coated glass fiber in the present invention can not only effectively reduce the molding shrinkage of polypropylene, but also improve the compatibility between glass fiber and polypropylene through the interaction between the compatibilizer and the coated TPU, improve the load transfer efficiency, and ultimately improve the reinforcing effect of glass fiber on polypropylene. At the same time, the coating of TPU and the glass fiber form a core-hard shell-soft structure, and this core-shell structure greatly improves the toughness of polypropylene.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention can make the obtained polypropylene wire have a lower molding shrinkage rate through the compounding of thermoplastic elastomer TPU coated glass fiber and compatibilizer system, and can print larger-sized 3D printed products with higher precision.

[0015] (2) The coating of thermoplastic elastomer TPU improves the compatibility between glass fiber and polypropylene, greatly increasing the filling amount of glass fiber. The products prepared by 3D printing of composite polypropylene materials have greatly improved mechanical properties. 3D printed polypropylene products can be used for the preparation of high-strength and high-toughness structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a scanning electron microscope image of the thermoplastic elastomer TPU coated glass fiber of the present invention. DETAILED DESCRIPTION

[0017] A preparation of a high-strength and tough polypropylene wire for 3D printing comprises the following steps: S1, mixing polypropylene, a compatibilizer, a tackifying resin and an antioxidant in proportion to obtain a mixture; S2, feeding the above mixture through the main feeding port of the twin-screw extruder, feeding the thermoplastic elastomer TPU coated glass fiber from the side feeding port, extruding, cooling and then pelletizing with a pelletizer to obtain a granular modified polypropylene composite material; S3. Extrude the obtained granular modified polypropylene composite material through a single screw extruder to obtain filamentous 3D printing polypropylene consumables, which are then wound into bundles and bagged.

[0018] The composition includes, by weight: 100 parts of polypropylene, 4 to 10 parts of a compatibilizer, 30 to 90 parts of thermoplastic elastomer TPU coated glass fiber, 2 to 10 parts of a tackifying resin, and 0.05 to 0.3 parts of an antioxidant.

[0019] The polypropylene is selected to be one or both of syndiotactic polypropylene (5-25 g / 10 min, melt flow rate test conditions: 230°C, 2.16 kg; melting temperature 150-190°C) and random polypropylene (20-40 g / 10 min, melt flow rate test conditions: 230°C, 2.16 kg; melting temperature 150-190°C).

[0020] The compatibilizer is a maleic anhydride grafted product, specifically including one or two of maleic anhydride grafted polypropylene and maleic anhydride grafted thermoplastic elastomer TPU.

[0021] The tackifying resin is one or more of terpene resin, hydrogenated rosin and petroleum resin.

[0022] The antioxidant is one or more of a hindered amine antioxidant, a hindered phenol antioxidant, a phosphite antioxidant, and a polymer antioxidant.

[0023] The tackifying resin is one or more of terpene resin, hydrogenated rosin and petroleum resin.

[0024] Furthermore, the preparation steps of the thermoplastic elastomer TPU coated glass fiber are as follows: 1) Add glass fiber to 1 mol / L NaOH aqueous solution, stir at room temperature for 2-6 h, then take out and dry; 2) Add the treated glass fiber in step 1) into a mixed solution containing polyester polyol, 1,4-butanediol (BDO), an organic tin catalyst and cyclohexanone, and stir evenly; 3) Add pure 4,4'-diphenylmethane diisocyanate (MDI) to the mixed solution in step 2), stir at high speed, protect with nitrogen and heat to 100 °C, and react for 2 to 6 hours; 4) The solution obtained in step 3) is diluted with cyclohexanone and then filtered. The filtered glass fiber is placed in a vacuum oven at 125° C. (vacuum degree is -90 KPa) and aged for 4 to 8 hours to prepare a thermoplastic elastomer TPU coated glass fiber.

[0025] The glass fiber has a mesh size of 50 to 300; the mass ratio of the glass fiber, polyester polyol, BDO, organotin catalyst and MDI is 100: (30 to 120): (10 to 40): (0.3 to 0.5): (30 to 90); the mass ratio of cyclohexanone to glass fiber in step 2) is (0.5 to 1.5): 1; and the mass ratio of cyclohexanone to glass fiber in step 4) is (1 to 3): 1.

[0026] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features well known in the art are not described.

[0027] In order to fully understand the present invention, a detailed structure will be presented in the following description. Obviously, the implementation of the present invention is not limited to the specific details familiar to those skilled in the art. The preferred embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other embodiments.

[0028] The maleic anhydride grafted thermoplastic elastomer TPU used in the following examples and comparative examples is manufactured by Dow Chemical Co., Ltd., model number 6851; The polyester polyols used in the following examples and comparative examples are produced by Jining Tangyi Chemical Co., Ltd., and the model number is XCP.

[0029] Example 1 The glass fiber was added to a 1 mol / L NaOH aqueous solution, stirred at room temperature for 3 h, filtered, and dried; then the treated glass fiber was added to a mixed solution containing polyester polyol, 1, 4-butanediol (BDO), an organic tin catalyst (dibutyltin dilaurate) and cyclohexanone, and stirred evenly. Then, pure 4,4'-diphenylmethane diisocyanate (MDI) was added to the mixed solution, stirred at high speed, and heated to 100 °C under nitrogen protection for 4 hours. The mass ratio of glass fiber, polyester polyol, BDO, organic tin catalyst, MDI and cyclohexanone in the mixed solution was 100:60:20:0.4:30:100; after the reaction was completed, cyclohexanone was added at a mass ratio of 1:1 to the glass fiber for dilution, filtered, and the obtained glass fiber was placed in a vacuum oven at 125 °C (vacuum degree of -90 KPa) for 8 hours to prepare thermoplastic elastomer TPU coated glass fiber.

[0030] According to weight, 50 parts of syndiotactic polypropylene, 50 parts of random polypropylene, 10 parts of terpene resin, 5 parts of maleic anhydride grafted polypropylene, 5 parts of maleic anhydride grafted thermoplastic elastomer TPU, and 0.15 parts of hindered amine antioxidant (antioxidant 3114) were added to the mixer for pre-mixing (mixing temperature was 30°C, speed was 300 rpm, and mixing time was 2 minutes). Then the pre-mixed materials were added from the feeder to the co-rotating parallel twin-screw extruder, and 30 parts of the prepared thermoplastic elastomer TPU coated glass fiber were added through the side feed port, melt extruded (screw speed was 400 rpm, feeder speed was 30 rpm; the temperature of each section of the extruder was 140-180°C, one zone was 150°C, and the other zones were 180°C), and the strands were water-dried and pelletized. The pellets are dried, fed into a single screw extruder from a feeder, melt-extruded (the temperature of each section of the extruder is 150-180°C, one section is 155°C, and the other sections are 180°C), drawn by a traction machine, and wound to obtain polypropylene wire for 3D printing.

[0031] Example 2 Thermoplastic elastomer TPU coated glass fiber was prepared according to the method shown in Example 1.

[0032] According to weight, 50 parts of syndiotactic polypropylene, 50 parts of random polypropylene, 10 parts of terpene resin, 5 parts of maleic anhydride grafted polypropylene, 5 parts of maleic anhydride grafted thermoplastic elastomer TPU, and 0.15 parts of hindered amine antioxidant (antioxidant 3114) were added to the mixer for pre-mixing (mixing temperature was 30°C, speed was 300 rpm, and mixing time was 2 minutes). Then the pre-mixed materials were added from the feeder to the co-rotating parallel twin-screw extruder, and 50 parts of the prepared thermoplastic elastomer TPU coated glass fiber were added through the side feed port, melt extruded (screw speed was 400 rpm, feeder speed was 30 rpm; the temperature of each section of the extruder was 140-180°C, one zone was 150°C, and the other zones were 180°C), and the strands were water-dried and pelletized. The pellets are dried, fed into a single screw extruder from a feeder, melt-extruded (the temperature of each section of the extruder is 150-180°C, one section is 155°C, and the other sections are 180°C), drawn by a traction machine, and wound to obtain polypropylene wire for 3D printing.

[0033] Example 3 Thermoplastic elastomer TPU coated glass fiber was prepared according to the method shown in Example 1.

[0034] According to weight, 50 parts of syndiotactic polypropylene, 50 parts of random polypropylene, 10 parts of terpene resin, 5 parts of maleic anhydride grafted polypropylene, 5 parts of maleic anhydride grafted thermoplastic elastomer TPU, and 0.15 parts of hindered amine antioxidant (antioxidant 3114) were added to the mixer for pre-mixing (mixing temperature was 30°C, speed was 300 rpm, and mixing time was 2 minutes). Then the pre-mixed materials were added from the feeder to the co-rotating parallel twin-screw extruder, and 70 parts of the prepared thermoplastic elastomer TPU coated glass fiber were added through the side feed port, melt extruded (screw speed was 400 rpm, feeder speed was 30 rpm; the temperature of each section of the extruder was 140-180°C, one zone was 150°C, and the other zones were 180°C), and the strands were water-dried and pelletized. The pellets are dried, fed into a single screw extruder from a feeder, melt-extruded (the temperature of each section of the extruder is 150-180°C, one section is 155°C, and the other sections are 180°C), drawn by a traction machine, and wound to obtain polypropylene wire for 3D printing.

[0035] Example 4 Thermoplastic elastomer TPU coated glass fiber was prepared according to the method shown in Example 1.

[0036] According to weight, 50 parts of syndiotactic polypropylene, 50 parts of random polypropylene, 10 parts of terpene resin, 5 parts of maleic anhydride grafted polypropylene, 5 parts of maleic anhydride grafted thermoplastic elastomer TPU, and 0.15 parts of hindered amine antioxidant (antioxidant 3114) were added to the mixer for pre-mixing (mixing temperature was 30°C, speed was 300 rpm, and mixing time was 2 minutes). Then the pre-mixed materials were added from the feeder to the co-rotating parallel twin-screw extruder, and 90 parts of the prepared thermoplastic elastomer TPU coated glass fiber were added through the side feed port, melt extruded (screw speed was 400 rpm, feeder speed was 30 rpm; the temperature of each section of the extruder was 140-180°C, one zone was 150°C, and the other zones were 180°C), and the strands were water-dried and pelletized. The pellets are dried, fed into a single screw extruder from a feeder, melt-extruded (the temperature of each section of the extruder is 150-180°C, one section is 155°C, and the other sections are 180°C), drawn by a traction machine, and wound to obtain polypropylene wire for 3D printing.

[0037] Comparative Example 1 According to weight, 50 parts of syndiotactic polypropylene, 50 parts of random polypropylene, 10 parts of terpene resin, 5 parts of maleic anhydride grafted polypropylene, 5 parts of maleic anhydride grafted thermoplastic elastomer TPU, and 0.15 parts of hindered amine antioxidant (antioxidant 3114) were added to the mixer for pre-mixing (mixing temperature was 30°C, speed was 300 rpm, and mixing time was 2 minutes). Then the pre-mixed materials were added from the feeder to the co-rotating parallel twin-screw extruder for melt extrusion (screw speed was 400 rpm, feeder speed was 30 rpm; the temperature of each section of the extruder was 140-180°C, one section was 150°C, and the other sections were 180°C), and the strands were water-dried and pelletized. The pellets are dried, fed into a single screw extruder from a feeder, melt-extruded (the temperature of each section of the extruder is 150-180°C, one section is 155°C, and the other sections are 180°C), drawn by a traction machine, and wound to obtain polypropylene wire for 3D printing.

[0038] Comparative Example 2 According to weight, 50 parts of syndiotactic polypropylene, 50 parts of random polypropylene, 10 parts of terpene resin, 5 parts of maleic anhydride grafted polypropylene, 5 parts of maleic anhydride grafted thermoplastic elastomer TPU, and 0.15 parts of hindered amine antioxidant (antioxidant 3114) were added to the mixer for pre-mixing (mixing temperature was 30°C, speed was 300 rpm, and mixing time was 2 minutes). Then the pre-mixed materials were added from the feeder to the co-rotating parallel twin-screw extruder, and 50 parts of glass fiber were added through the side feed port, melt extruded (screw speed was 400 rpm, feeder speed was 30 rpm; the temperature of each section of the extruder was 140-180°C, one zone was 150°C, and the other zones were 180°C), and the strands were water-dried and pelletized. The pellets are dried, fed into a single screw extruder from a feeder, melt-extruded (the temperature of each section of the extruder is 150-180°C, one section is 155°C, and the other sections are 180°C), drawn by a traction machine, and wound to obtain polypropylene wire for 3D printing.

[0039] The wire prepared above was printed into tensile specimens and notched impact specimens by FDM 3D printer. The wire prepared above was pelletized and injection molded to prepare tensile specimens and notched impact specimens. The performance of 3D printed products and injection molded products was tested, and the test results are shown in Table 1.

[0040] Table 1 From the comparison of the results in Table 1, it can be seen that with the increase of the content of thermoplastic elastomer TPU coated glass fiber in the polypropylene wire, the compatibility between the glass fiber and the polypropylene matrix is ​​effectively improved, and the transmission efficiency of the stress load is improved, thereby reducing the molding shrinkage and improving the performance of the 3D printed product.

[0041] In contrast, the polypropylene wire prepared by the glass fiber system coated with thermoplastic elastomer TPU (Comparative Example 1) can be 3D printed, but its molding shrinkage is high, and the printed product is rough, resulting in poor tensile strength and impact strength. The polypropylene wire prepared by adding unmodified glass fiber (Comparative Example 2) has poor compatibility with polypropylene and poor dispersion due to the unmodified glass fiber. The diameter uniformity of the 3D printed wire is poor, and the shrinkage of polypropylene is higher than that of the thermoplastic elastomer TPU coated glass fiber reinforced polypropylene material, but its tensile strength and impact strength are lower than those of the thermoplastic elastomer TPU coated glass fiber reinforced polypropylene material (Example 2) at the same addition amount, which shows that the thermoplastic elastomer TPU coating treatment can significantly improve the reinforcing and toughening effect of glass fiber on polypropylene material.

[0042] In summary, the present invention prepares a high-strength and high-toughness polypropylene material by compounding thermoplastic elastomer TPU coated glass fiber with polypropylene, and uses it for 3D printing, thereby realizing 3D printing of high-strength and high-toughness polypropylene.

[0043] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A high-strength and high-toughness polypropylene 3D printing wire, characterized by: The raw materials used include, by weight: 100 parts of polypropylene, 4-10 parts of compatibilizer, 30-90 parts of thermoplastic elastomer TPU coated glass fiber, 2-10 parts of tackifying resin, and 0.05-0.3 parts of antioxidant.

2. A high-strength and high-toughness polypropylene 3D printing wire according to claim 1, characterized in that: The polypropylene is selected from one or both of syndiotactic polypropylene and atactic polypropylene.

3. A high-strength and high-toughness polypropylene 3D printing wire according to claim 1, characterized in that: The compatibilizer is one or both of maleic anhydride grafted polypropylene and maleic anhydride grafted thermoplastic elastomer TPU.

4. A high-strength and high-toughness polypropylene 3D printing wire according to claim 1, characterized in that: The tackifying resin is one or more of terpene resin, hydrogenated rosin and petroleum resin.

5. The high-strength and high-toughness polypropylene 3D printing wire according to claim 1, characterized in that: The antioxidant is one or more of a hindered amine antioxidant, a hindered phenol antioxidant, a phosphite antioxidant, and a polymer antioxidant.

6. A high-strength and high-toughness polypropylene 3D printing wire according to claim 1, characterized in that: The preparation method of the thermoplastic elastomer TPU coated glass fiber comprises the following steps: 1) Add glass fiber to 1 mol / L NaOH aqueous solution, stir at room temperature for 2-6 h, then take out and dry; 2) adding the treated glass fiber in step 1) into a mixed solution containing polyester polyol, 1,4-butanediol, an organic tin catalyst and cyclohexanone, and stirring evenly; 3) Add pure 4,4'-diphenylmethane diisocyanate MDI to the mixed solution in step 2), stir at high speed, protect with nitrogen and heat to 100 °C, and react for 2 to 6 hours; 4) diluting the solution obtained in step 3) with cyclohexanone, and then filtering, and placing the filtered glass fiber in a vacuum oven at 125° C. for aging for 4 to 8 hours to prepare a thermoplastic elastomer TPU coated glass fiber; The glass fiber has a mesh size of 50 to 300; the mass ratio of the glass fiber, polyester polyol, 1,4-butanediol, organic tin catalyst and MDI is 100: (30 to 120): (10 to 40): (0.3 to 0.5): (30 to 90); the mass ratio of cyclohexanone to glass fiber in step 2) is (0.5 to 1.5): 1; the mass ratio of cyclohexanone to glass fiber in step 4) is (1 to 3):

1.

7. The method for preparing a high-strength and high-toughness polypropylene 3D printing wire according to claim 1, characterized in that: The following steps are involved: S1, mixing polypropylene, a compatibilizer, a tackifying resin and an antioxidant in proportion to obtain a mixture; S2, feeding the above mixture through the main feeding port of the twin-screw extruder, feeding the thermoplastic elastomer TPU coated glass fiber from the side feeding port, extruding, cooling and then pelletizing with a pelletizer to obtain a granular modified polypropylene composite material; S3. Extrude the obtained granular modified polypropylene composite material through a single screw extruder to obtain filamentous polypropylene 3D printing wire, which is then wound into bundles and bagged.

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