High-precision low-thermal-conductivity polypropylene porous structure product formed by 3D printing and preparation method of high-precision low-thermal-conductivity polypropylene porous structure product

Abstract

The invention discloses a high-precision low-thermal-conductivity polypropylene porous structure product formed by 3D printing and a preparation method thereof, and an ethylene-vinyl acetate copolymer / polypropylene wire rod is prepared by blending an ethylene-vinyl acetate copolymer and polypropylene. An ethylene-vinyl acetate copolymer / polypropylene product is obtained through 3D printing forming, then the ethylene-vinyl acetate copolymer is removed through tetrahydrofuran, and the 3D printing forming polypropylene porous structure product is prepared. The raw materials are easy to obtain, the preparation process is simple and efficient, and the cost is low. Through blending of the ethylene-vinyl acetate copolymer and polypropylene, the 3D printing performance of polypropylene is improved, and a high-precision polypropylene printed product is obtained. After the ethylene-vinyl acetate copolymer is removed by using tetrahydrofuran, a porous network structure is formed in a polypropylene printed product, so that the polypropylene printed product has a relatively low heat conductivity coefficient, and the polypropylene printed product can be applied to multiple fields such as heat insulation, sound insulation and wave absorption.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a high-precision low-thermal-conductivity porous polypropylene structure product formed by 3D printing and a preparation method thereof. Background Art

[0002] Polypropylene materials have been widely used in many fields due to their diverse raw material sources, mature preparation processes, low costs, high melting points and softening points, low densities, and excellent comprehensive properties such as heat resistance, water resistance, and chemical stability. In the field of 3D printing, the application of polypropylene materials is also becoming more and more in-depth.

[0003] However, due to crystallization and thermal expansion coefficient, polypropylene has a large molding shrinkage rate, and products are prone to warping during the printing process and are difficult to form. Currently, various developed modification methods mainly focus on reducing the crystallinity of polypropylene (such as CN 103739954B, CN 108641197 B, CN110437538 B, CN 109608762 B, CN 116218123 A, and CN 110628130 B, etc.), and obvious effects have been achieved.

[0004] Therefore, in 3D printing forming, the performance of polypropylene has been initially improved. However, in its applications, some properties of polypropylene have not been significantly manifested. Such as lower density and better toughness, etc. Summary of the Invention

[0005] In order to further demonstrate an application advantage of polypropylene in 3D printing forming, the present invention provides a high-precision low-thermal-conductivity porous polypropylene structure product formed by 3D printing and a preparation method thereof. The component raw materials of the present invention are easy to obtain, the preparation process is simple and efficient, and the cost is low. By blending ethylene-vinyl acetate copolymer with polypropylene, the 3D printing performance of polypropylene is improved, and a high-precision polypropylene printed product is obtained. After removing the ethylene-vinyl acetate copolymer with tetrahydrofuran, a porous network structure is formed in the polypropylene printed product, making the polypropylene product have a lower thermal conductivity, and thus it can be used in applications such as heat insulation, sound insulation, and wave absorption in multiple fields.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A high-precision low-thermal-conductivity porous polypropylene structure product formed by 3D printing, the raw materials used in which include, by weight: 100 parts of polypropylene, 60 - 120 parts of ethylene-vinyl acetate copolymer, 20 - 60 parts of filler, and 0.05 - 0.3 parts of antioxidant.

[0007] Furthermore, a high-precision and low-thermal-conductivity polypropylene porous structure product formed by 3D printing, wherein the polypropylene is selected from one or two of syndiotactic polypropylene and atactic polypropylene.

[0008] Furthermore, a high-precision and low-thermal-conductivity polypropylene porous structure product formed by 3D printing, wherein the content of vinyl acetate in the ethylene-vinyl acetate copolymer is 15wt% - 40wt%.

[0009] Furthermore, a high-precision and low-thermal-conductivity polypropylene porous structure product formed by 3D printing, wherein the filler is one or several of talcum powder, calcium carbonate, silicon dioxide and glass fiber.

[0010] Furthermore, a high-precision and low-thermal-conductivity polypropylene porous structure product formed by 3D printing, wherein the antioxidant is one or several of hindered amine antioxidants, hindered phenol antioxidants, phosphite antioxidants, and polymer antioxidants.

[0011] Furthermore, a preparation method of a high-precision and low-thermal-conductivity polypropylene porous structure product formed by 3D printing includes the following steps: 1) Mix polypropylene, ethylene-vinyl acetate copolymer, filler and antioxidant in proportion to obtain a mixture; 2) Feed the above mixture into the feeding port of a twin-screw extruder, extrude, cool and pelletize with a pelletizer to obtain an ethylene-vinyl acetate copolymer / polypropylene composite material; 3) Extrude the ethylene-vinyl acetate copolymer / polypropylene composite material through a single-screw extruder to prepare a filamentous 3D printing ethylene-vinyl acetate copolymer / polypropylene consumable, wind it into bundles and pack it in bags; 4) Use the above filamentous 3D printing ethylene-vinyl acetate copolymer / polypropylene consumable for FDM printing to prepare a 3D printed ethylene-vinyl acetate copolymer / polypropylene product; 5) Put the 3D printed ethylene-vinyl acetate copolymer / polypropylene product into a Soxhlet extractor, extract it with tetrahydrofuran to remove the ethylene-vinyl acetate copolymer, and then dry it to prepare a 3D printed polypropylene porous structure product.

[0012] In the present invention, the compounding of the ethylene-vinyl acetate copolymer can not only effectively reduce the molding shrinkage rate of polypropylene and improve the molding precision of polypropylene, but also the relatively low compatibility between the ethylene-vinyl acetate copolymer and polypropylene enables the ethylene-vinyl acetate copolymer and polypropylene to form a double-continuous phase structure. After removing the ethylene-vinyl acetate copolymer with tetrahydrofuran, a porous continuous structure is formed in the polypropylene 3D printed product.

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1)Through the compounding of ethylene-vinyl acetate copolymer, the obtained polypropylene wire can have a low molding shrinkage rate without adding other large amounts of fillers, and can print high-precision and large-sized 3D printed polypropylene products.

[0014] (2)The low compatibility between ethylene-vinyl acetate copolymer and polypropylene enables the formation of a bicontinuous phase structure between ethylene-vinyl acetate copolymer and polypropylene. After removing the ethylene-vinyl acetate copolymer by tetrahydrofuran, a porous continuous structure is formed in the polypropylene 3D printed product. This continuous porous structure endows the 3D printed polypropylene product with good heat insulation, sound insulation, wave absorption and other properties. Description of the Drawings

[0015] Figure 1 It is a scanning electron micrograph of the tensile cross-section of a high-precision and low-thermal-conductivity polypropylene porous structure product formed by 3D printing in Example 1 of the present invention. Detailed Description of the Invention

[0016] In order to further explain the technical solution of the present invention, the present invention will be elaborated in detail through specific examples below.

[0017] Example 1 By weight, 100 parts of random polypropylene, 60 parts of ethylene-vinyl acetate copolymer, 20 parts of talcum powder, and 0.15 part of hindered amine antioxidant (antioxidant 5057) were mixed, and added from the feeder to a co-rotating parallel twin-screw extruder, and melt-extruded (the screw speed was 400 revolutions per minute, and the feeder speed was 30 revolutions per minute; the temperatures of each section of the extruder were 140-180 °C, where the first zone was 150 °C and the other zones were 180 °C), and then strand-passed through water and pelletized. The above pellets were dried, added from the feeder to a single-screw extruder, and melt-extruded (the temperatures of each section of the extruder were 150-180 °C, where the first zone was 155 °C and the other zones were 180 °C), and then drawn and wound by a traction machine to obtain an ethylene-vinyl acetate copolymer / polypropylene wire for 3D printing.

[0018] The above wire was formed by FDM printing to prepare a 3D printed ethylene-vinyl acetate copolymer / polypropylene product. The formed product was placed in a Soxhlet extractor and extracted with tetrahydrofuran at 70 °C, and then dried at 70 °C for 12 h to obtain a 3D printed polypropylene porous structure product.

[0019] Example 2 By weight parts, 100 parts of random polypropylene, 80 parts of ethylene-vinyl acetate copolymer, 20 parts of talcum powder, and 0.15 part of hindered amine antioxidant (antioxidant 5057) are mixed and added from a feeder to a co-rotating parallel twin-screw extruder for melt extrusion (the screw speed is 400 revolutions per minute and the feeder speed is 30 revolutions per minute; the temperatures of each section of the extruder are 140 - 180 °C, where the temperature of zone 1 is 150 °C and the temperatures of other zones are 180 °C), followed by strand passing through water and pelletizing. The above pellets are dried and added from a feeder to a single-screw extruder for melt extrusion (the temperatures of each section of the extruder are 150 - 180 °C, where the temperature of zone 1 is 155 °C and the temperatures of other zones are 180 °C), then drawn and stretched by a tractor and wound to obtain an ethylene-vinyl acetate copolymer / polypropylene wire for 3D printing.

[0020] The above wire is formed by FDM printing to prepare a 3D printed ethylene-vinyl acetate copolymer / polypropylene product. The formed product is placed in a Soxhlet extractor and extracted with tetrahydrofuran at 70 °C, and then dried at 70 °C for 12 h to obtain a 3D printed porous polypropylene structure product.

[0021] Example 3 By weight parts, 100 parts of random polypropylene, 100 parts of ethylene-vinyl acetate copolymer, 20 parts of talcum powder, and 0.15 part of hindered amine antioxidant (antioxidant 5057) are mixed and added from a feeder to a co-rotating parallel twin-screw extruder for melt extrusion (the screw speed is 400 revolutions per minute and the feeder speed is 30 revolutions per minute; the temperatures of each section of the extruder are 140 - 180 °C, where the temperature of zone 1 is 150 °C and the temperatures of other zones are 180 °C), followed by strand passing through water and pelletizing. The above pellets are dried and added from a feeder to a single-screw extruder for melt extrusion (the temperatures of each section of the extruder are 150 - 180 °C, where the temperature of zone 1 is 155 °C and the temperatures of other zones are 180 °C), then drawn and stretched by a tractor and wound to obtain an ethylene-vinyl acetate copolymer / polypropylene wire for 3D printing.

[0022] The above wire is formed by FDM printing to prepare a 3D printed ethylene-vinyl acetate copolymer / polypropylene product. The formed product is placed in a Soxhlet extractor and extracted with tetrahydrofuran at 70 °C, and then dried at 70 °C for 12 h to obtain a 3D printed porous polypropylene structure product.

[0023] Example 4 By weight parts, 100 parts of atactic polypropylene, 120 parts of ethylene-vinyl acetate copolymer, 20 parts of talcum powder, and 0.15 part of hindered amine antioxidant (antioxidant 5057) are mixed and added from a feeder into a co-rotating parallel twin-screw extruder for melt extrusion (the screw speed is 400 revolutions per minute, and the feeder speed is 30 revolutions per minute; the temperatures of each section of the extruder are 140 - 180 °C, where the temperature of zone 1 is 150 °C and the temperatures of other zones are 180 °C), and then strand passing through water and pelletizing. The above pellets are dried and added from a feeder into a single-screw extruder for melt extrusion (the temperatures of each section of the extruder are 150 - 180 °C, where the temperature of zone 1 is 155 °C and the temperatures of other zones are 180 °C), and then drawn into filaments by a traction machine and wound to obtain an ethylene-vinyl acetate copolymer / polypropylene wire for 3D printing.

[0024] The above wire is formed by FDM printing to prepare a 3D printed ethylene-vinyl acetate copolymer / polypropylene product. The formed product is placed in a Soxhlet extractor and extracted with tetrahydrofuran at 70 °C, and then taken out and dried at 70 °C for 12 h to obtain a 3D printed porous polypropylene structure product.

[0025] Comparative Example 1 By weight parts, 100 parts of atactic polypropylene, 20 parts of talcum powder, and 0.15 part of hindered amine antioxidant (antioxidant 5057) are mixed and added from a feeder into a co-rotating parallel twin-screw extruder for melt extrusion (the screw speed is 400 revolutions per minute, and the feeder speed is 30 revolutions per minute; the temperatures of each section of the extruder are 140 - 180 °C, where the temperature of zone 1 is 150 °C and the temperatures of other zones are 180 °C), and then strand passing through water and pelletizing. The above pellets are dried and added from a feeder into a single-screw extruder for melt extrusion (the temperatures of each section of the extruder are 150 - 180 °C, where the temperature of zone 1 is 155 °C and the temperatures of other zones are 180 °C), and then drawn into filaments by a traction machine and wound to obtain an ethylene-vinyl acetate copolymer / polypropylene wire for 3D printing.

[0026] The above wire is formed by FDM printing to prepare a 3D printed polypropylene product.

[0027] Comparative Example 2 By weight parts, 100 parts of random polypropylene, 20 parts of talcum powder, and 0.15 part of hindered amine antioxidant (antioxidant 5057) are mixed and added from a feeder to a co-rotating parallel twin-screw extruder for melt extrusion (the screw speed is 400 revolutions per minute, and the feeder speed is 30 revolutions per minute; the temperatures of each section of the extruder are 140 - 180 °C, where the first zone is 150 °C and the other zones are 180 °C), and then strand water cutting and pelletizing are carried out. The above pellets are dried and added from a feeder to a single-screw extruder for melt extrusion (the temperatures of each section of the extruder are 150 - 180 °C, where the first zone is 155 °C and the other zones are 180 °C), and then drawn and drawn by a tractor and wound to obtain an ethylene-vinyl acetate copolymer / polypropylene wire.

[0028] The above wire is injection molded to prepare an injection molded polypropylene product.

[0029] The wire prepared above is printed into tensile specimens and thermal conductivity test specimens by an FDM 3D printer for performance testing, and the test results are shown in Table 1.

[0030] Table 1 Note: Comparative Example 2 is a test of an injection molded specimen.

[0031] It can be seen from the comparison of the results in Table 1 that the addition of ethylene-vinyl acetate copolymer significantly improves the 3D printing performance of polypropylene. The polypropylene materials in the examples can all complete printing completely and with high precision, while the polypropylene without adding ethylene-vinyl acetate copolymer cannot be printed completely due to warping under the same conditions.

[0032] With the increase of the content of ethylene-vinyl acetate copolymer, more pore structures are generated, thus reducing the mechanical strength of the 3D printed polypropylene porous structure product, but the lowest tensile strength is still above 5 MPa. Obviously, the introduction of continuous pore structures significantly reduces the density of the 3D printed polypropylene porous structure product, making the product lighter. And the introduction of continuous pore structures also significantly reduces the thermal conductivity of the polypropylene 3D printed product, making it have certain heat insulation performance.

[0033] In summary, the present invention improves the 3D printing performance of polypropylene by blending ethylene-vinyl acetate copolymer with polypropylene to obtain a high-precision polypropylene printed product. After removing the ethylene-vinyl acetate copolymer with tetrahydrofuran, a porous network structure is formed in the polypropylene printed product, making the polypropylene product have a lower thermal conductivity, and thus it can be used in many fields such as heat insulation, sound insulation, and wave absorption.

[0034] The foregoing has shown and described 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 all technical solutions obtained by means of equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A high-precision and low-thermal-conductivity polypropylene porous structure product formed by 3D printing, characterized in that: The raw materials used include, by weight parts: 100 parts of polypropylene, 60 - 120 parts of ethylene - vinyl acetate copolymer, 20 - 60 parts of filler, and 0.05 - 0.3 parts of antioxidant.

2. The high-precision and low-thermal-conductivity polypropylene porous structure product formed by 3D printing according to claim 1, wherein: The polypropylene selected is one or two of syndiotactic polypropylene and atactic polypropylene.

3. A high-precision and low-thermal-conductivity polypropylene porous structure product formed by 3D printing according to claim 1, characterized in that: The content of vinyl acetate in the ethylene - vinyl acetate copolymer is 15wt% - 40wt%.

4. A high-precision and low-thermal-conductivity polypropylene porous structure product formed by 3D printing according to claim 1, characterized in that: The filler is one or several of talcum powder, calcium carbonate, silica, and glass fiber.

5. A high-precision and low-thermal-conductivity polypropylene porous structure product formed by 3D printing according to claim 1, characterized in that: The antioxidant is one or several of hindered amine antioxidants, hindered phenol antioxidants, phosphite antioxidants, and polymer antioxidants.

6. The preparation method of a high-precision and low-thermal-conductivity polypropylene porous structure product formed by 3D printing according to claim 1, characterized in that: It includes the following steps: 1) Mix polypropylene, ethylene - vinyl acetate copolymer, filler, and antioxidant in proportion to obtain a mixture; 2) Feed the above - mentioned mixture into the feeding port of a twin - screw extruder, extrude, cool, and then pelletize with a pelletizer to obtain an ethylene - vinyl acetate copolymer / polypropylene composite material; 3) Extrude the ethylene - vinyl acetate copolymer / polypropylene composite material through a single - screw extruder to produce a filamentous 3D - printing ethylene - vinyl acetate copolymer / polypropylene consumable, wind it into bundles and package it in bags; 4) Use the above - mentioned filamentous 3D - printing ethylene - vinyl acetate copolymer / polypropylene consumable for FDM printing to prepare a 3D - printed ethylene - vinyl acetate copolymer / polypropylene product; 5) Place the 3D - printed ethylene - vinyl acetate copolymer / polypropylene product in a Soxhlet extractor, extract it with tetrahydrofuran to remove the ethylene - vinyl acetate copolymer, and then dry it to prepare a 3D - printed porous polypropylene structure product.

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