3D printing controllable foaming TPU material and preparation method and application thereof

Abstract

The invention discloses a 3D printing controllable foaming TPU material and a preparation method and application thereof.The preparation method of the TPU material comprises the steps that TPU, a TPU surface modification additive, a foaming agent and an alcohol fluid are mixed and then subjected to melt extrusion, cooling, strip forming and rolling, and the 3D printing controllable foaming TPU material is obtained; wherein the alcohol fluid is one or a mixture of more of polyethylene glycol, polypropylene glycol, glycerol, ethylene glycol, 1, 2-propylene glycol, sorbitol and 1, 4-butanediol; the foaming temperature of the TPU material is 170-220 DEG C, the foaming ratio is 1-5 times, the tensile strength is greater than or equal to 15 MPa, and the elongation at break is greater than or equal to 400%. The processing temperature is reduced by introducing the alcohol fluid in the first processing process, so that the foaming agent with lower foaming temperature can be used, the printing temperature is finally reduced, the mechanical property of the material is improved, and the foaming ratio in the 3D printing process is controllable in the range of 1-5 times.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of foamed TPU, in particular to a method for preparing 3D printing controllable foamed TPU material by alcohol fluid extrusion. BACKGROUND

[0002] With the continuous development of 3D printing technology, as a common 3D printing technology, fused deposition modeling (FDM) has been widely used in many fields due to its low cost, simple operation and wide application of materials. However, the existing FDM printing materials still have some limitations in performance and application.

[0003] Thermoplastic polyurethane (TPU) is a kind of high molecular material with high toughness, wear resistance, oil resistance and other characteristics. The foamed material has the advantages of light weight, air permeability, environmental protection and good rebound, and is widely used in packaging, industry, transportation, daily necessities, medical products and other fields. The existing TPU foaming process is intermittent foaming and continuous foaming. The existing continuous foaming process is to melt and extrude the foaming agent and TPU at a high temperature of 350-360 DEG C, and a high-temperature foaming agent is used. There are two problems: (1) the high-temperature foaming agent (such as barium azodicarboxylate, trihydrazine-based s-triazine) is toxic and harmful; (2) the foamed TPU obtained at a high temperature reduces the mechanical properties of the material; thus, the TPU material has problems such as high printing temperature, difficult accurate control of foaming ratio and unstable mechanical properties of the material in the process of fused deposition 3D printing, which limits its further expansion in high-end application fields. SUMMARY

[0004] The first purpose of the application is to provide a TPU material with reduced foaming temperature, improved material mechanical properties and accurately controllable foaming ratio in 3D printing; the second purpose of the application is to provide a preparation method of the TPU material; and the third purpose of the application is to provide application of the TPU material in 3D printing.

[0005] The preparation method of the 3D printing controllable foamed TPU material provided by the application comprises the following steps: mixing TPU, a TPU surface modification aid, a foaming agent and an alcohol fluid, and then melt-extruding, cooling, forming a strip and winding to obtain a 3D printing controllable foamed TPU material; wherein the alcohol fluid is one or more of polyethylene glycol (PEG), polypropylene glycol (PPG), glycerol, ethylene glycol, 1,2-propanediol, sorbitol and 1,4-butanediol.

[0006] Preferably, the amount of the alcohol fluid is 1-2% of the mass of the TPU. The alcohol fluid is introduced into the foaming agent, and the alcohol fluid has the advantages of enhancing dispersibility and reducing material processing temperature, and effectively ensures that the foaming agent does not foam in the processing process.

[0007] Preferably, the foaming agent is one or more of azodicarbonamide (AC), azobisisobutyronitrile (AIBN) or sodium bicarbonate. The foaming agent of the present application has a foaming temperature of 170-220℃, low foaming temperature and is non-toxic and harmless.

[0008] Preferably, the melt extrusion temperature is 150-220℃.

[0009] Preferably, the screw rotation speed of the melt extrusion is 50-200 rpm and the melt extrusion reaction time is 5-20 minutes.

[0010] Preferably, the TPU surface modification aid is one or more of silane coupling agent, titanate coupling agent or maleic anhydride grafting agent, and the amount is 0.5%-5% of the mass of the TPU particles. The interface aid improves the surface properties of the TPU material and strengthens the dispersion of the foaming agent in the TPU material.

[0011] Preferably, the cooling method is air cooling or water cooling, and the cooling rate is 10-50℃ / min.

[0012] The 3D printing controllable foaming TPU material prepared by the preparation method of the present application.

[0013] The foaming temperature of the TPU material is 170-220℃; the foaming ratio is 1-5 times; the tensile strength is ≥15 MPa; the elongation at break is ≥400%; and the density is 0.5-0.9 g / cm 3 The present application realizes that the foaming agent does not foam in the processing process by reducing the processing temperature of the TPU material, and the mechanical properties of the material can be significantly improved, and the foaming ratio of the material in the 3D printing process is controllable.

[0014] The TPU material of the present application in the application of 3D printing.

[0015] The application method is that the TPU material is used in a fused deposition type 3D printer, the printing temperature is 180℃-240℃, and the printing speed is 60-200 mm / s. The precise control of the foaming ratio can be realized by adjusting the printing temperature and layer height.

[0016] Inventive mechanism: The present application optimizes the dispersibility and compatibility of the foaming agent in the TPU matrix through alcohol fluid assisted processing, and has excellent plasticizing effect on TPU, improves the processing characteristics of TPU particles, effectively ensures that the foaming agent does not foam in the first processing process, realizes the foaming of TPU material in the 3D printing process, realizes the dynamic adjustment of the foaming ratio by accurately controlling the 3D printing parameters (extrusion temperature, extrusion speed, etc.), and the foaming temperature is reduced, and the mechanical properties of the material are significantly improved. Compared with the traditional foaming process, the present application combines the continuous processing advantages of the double screw extruder, significantly improves the production efficiency and material performance consistency.

[0017] Beneficial effects: Compared with the prior art, the present application has the following obvious advantages: (1) the foaming temperature of the TPU material of the present application is low, the mechanical properties are significantly improved, and the foaming ratio in the 3D printing process is controllable in the range of 1-5 times; (2) the TPU material has excellent mechanical properties: the material density is 0.5-0.9 g / cm 3 , the tensile strength is ≥15 MPa, and the elongation at break is ≥400%; (2) the TPU material of the present application can be efficiently and continuously produced: the use of double screw extruder realizes continuous production, significantly reduces energy consumption and cost; (3) the TPU material of the present application has wide applicability: the material is suitable for fused deposition 3D printer, the printing temperature is 180-240℃, the printing speed is 60-200mm / s, and can be widely used in the fields of flexible cushioning materials and biomedical stents. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The cell survival rate chart after the TPU materials prepared in Examples 1-4 and Comparative Examples 1-2 were co-cultured with MC3T3-E1 cells for 48 hours. DETAILED DESCRIPTION

[0019] The technical solutions of the present application will be further described below in combination with examples.

[0020] Example 1

[0021] The 3D printing controllable foaming TPU material of the present application is prepared by the following method:

[0022] Take azodicarbonamide (AC) 5g, ethylene glycol 5g, 95A TPU 500g, and silane coupling agent KH560 5g, mix uniformly, then put the mixture into a co-rotating intermeshing double screw extruder with a diameter of 35mm and a length-diameter ratio of 48, the screw rotation speed is 120rpm, the extrusion temperature is 175℃, and the melt blending reaction is carried out. At the same time of extrusion reaction, start the water circulating vacuum pump to remove the volatile gas generated in the reaction, and the extrusion product is water-cooled and granulated to obtain TPU foaming granules.

[0023] The product of the above extrusion blending granulation is placed in an oven at 80°C for 4 hours, and then added to a FLD-25A4 type 3D printing filament extruder (Fland Machinery Co., Ltd. of Zhangjiagang City), the extrusion speed is 1200 rpm, the extrusion temperature is 175°C, and after water cooling, air drying, and winding into TPU foaming consumables with a diameter of 1.75 mm, the hardness (Shore hardness tester) of the wire is tested, the sample is prepared by a 3D printer according to the standard (GB / T1040.2-2022, 5A type sample, the tensile speed is 50 mm / min), the filling rate is 100%, the filling angle is 0° / 90°, and the mechanical property test is carried out (the results are shown in Table 1), and in addition, the foaming ratio is tested under different 3D printing temperatures and layer heights (the results are shown in Table 2).

[0024] Example 2

[0025] The 3D printing controllable foaming TPU material of the application has the following preparation method:

[0026] 7.5 g of azodicarbonamide (AC), 10 g of 1,2-propanediol, 500 g of 95A TPU, and 5 g of silane coupling agent KH560 are weighed and uniformly mixed; then the mixture is added into a co-rotating intermeshing twin-screw extruder with a diameter of 35 mm and a length-diameter ratio of 48, the screw rotation speed is 120 rpm, the extrusion temperature is 175°C, and the melt blending reaction is carried out, at the same time, a water circulating vacuum pump is started to remove the volatile gas generated in the reaction by vacuum, and the extrusion product is water-cooled and granulated to obtain TPU foaming granules.

[0027] The product of the above extrusion blending granulation is placed in an oven at 80°C for 4 hours, and then added to a FLD-25A4 type 3D printing filament extruder (Fland Machinery Co., Ltd. of Zhangjiagang City), the extrusion speed is 1200 rpm, the extrusion temperature is 175°C, and after water cooling, air drying, and winding into TPU foaming consumables with a diameter of 1.75 mm, the hardness (Shore hardness tester) of the wire is tested, the sample is prepared by a 3D printer according to the standard (GB / T1040.2-2022, 5A type sample, the tensile speed is 50 mm / min), the filling rate is 100%, the filling angle is 0° / 90°, and the mechanical property test is carried out (the results are shown in Table 1), and in addition, the foaming ratio is tested under different 3D printing temperatures and layer heights (the results are shown in Table 2).

[0028] Example 3

[0029] The 3D printing controllable foaming TPU material of the application has the following preparation method:

[0030] Take azodicarbonamide (AC) 10g, ethylene glycol 10g, 95ATPU 500g, phthalate coupling agent Tyzor726 5g, mix evenly; then the mixture is added together into the same direction meshing double screw extruder with diameter of 35mm and length-diameter ratio of 48, the screw rotation speed is 120rpm, the extrusion temperature is 170℃, melt blending reaction is carried out, the water circulating vacuum pump is started at the same time of extrusion reaction, the volatile gas generated in the reaction is removed by vacuum, the extrusion product is water-cooled, granulated, and TPU foaming granular material is obtained.

[0031] The product of the above extrusion blending granulation is placed in an oven at 80℃ for 4 hours, and then added to the FLD-25A4 type 3D printing filament extruder (Zhangjiagang Fland Machinery Co., Ltd.), the extrusion rotation speed is 1200rpm, the extrusion temperature is 170℃, and the TPU foaming consumables with diameter of 1.75mm are obtained after water cooling, air drying and winding. The hardness (Shore hardness tester) of the wire is tested, the sample is prepared by 3D printer according to the standard (GB / T1040.2-2022, 5A type sample, tensile speed is 50mm / min), the filling rate is 100%, the filling angle is 0° / 90°, and the mechanical property test is carried out (the results are shown in Table 1), in addition, the foaming ratio is tested under different 3D printing temperature conditions (the results are shown in Table 2).

[0032] Example 4

[0033] The 3D printing controllable foaming TPU material of the application has the preparation method:

[0034] Take azodicarbonamide (AC) 10g, ethylene glycol 10g, 95ATPU 500g, TPU-based red master batch 10g, phthalate coupling agent Tyzor726 5g, mix evenly; then the mixture is added together into the same direction meshing double screw extruder with diameter of 35mm and length-diameter ratio of 48, the screw rotation speed is 120rpm, the extrusion temperature is 170℃, melt blending reaction is carried out, the water circulating vacuum pump is started at the same time of extrusion reaction, the volatile gas generated in the reaction is removed by vacuum, the extrusion product is water-cooled, granulated, and TPU foaming red granular material is obtained.

[0035] The product of the above extrusion blending granulation was placed in an oven at 80°C for 4 hours, and then added to a FLD-25A4 type 3D printing filament extruder (Fland Machinery Co., Ltd. of Zhangjiagang), the extrusion speed was 1200 rpm, the extrusion temperature was 170°C, and after water cooling, air drying, and winding into a TPU foamed red consumable with a diameter of 1.75 mm, the hardness (Shore hardness tester) of the wire was tested, the sample was prepared by a 3D printer according to the standard (GB / T1040.2-2022, 5A type sample, tensile speed was 50 mm / min), the filling rate was 100%, the filling angle was 0° / 90°, and the mechanical property test was carried out (the results are shown in Table 1), in addition, the foaming ratio was tested under different 3D printing temperatures (the results are shown in Table 2).

[0036] Comparative Example 1

[0037] On the basis of Example 1, no alcohol fluid was added, the material was foamed during the melt blending extrusion process, and was directly used for Shore hardness test without printing in the printer (the results are shown in Table 1).

[0038] Comparative Example 2

[0039] The preparation method is as follows: pure TPU particles were placed in an oven at 80°C for 4 hours, and then added to a FLD-25A4 type 3D printing filament extruder (Fland Machinery Co., Ltd. of Zhangjiagang), the extrusion speed was 1200 rpm, the extrusion temperature was 170°C, and after water cooling, air drying, and winding into a TPU consumable with a diameter of 1.75 mm, the hardness (Shore hardness tester) of the wire was tested, the sample was prepared by a 3D printer according to the standard (GB / T1040.2-2022, 5A type sample, tensile speed was 50 mm / min), the filling rate was 100%, the filling angle was 0° / 90°, and the mechanical property test was carried out (the results are shown in Table 1).

[0040] Table 1 Shore hardness (Shore A) of TPU foamed wire

[0041] Serial number Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Shore hardness 65A 95A 94A 94A 92A 92A Tensile strength 10 MPa 38 MPa 34 MPa 34 MPa 32 MPa 32 MPa Elongation at break 230％ 430％ 440％ 443％ 456％ 462％

[0042] From the Shore hardness A test results in Table 1, it can be seen that the hardness of the foamed TPU wire in Examples 1-4 is moderate and stable, the Shore hardness value is concentrated between 92A and 94A, which is much better than Comparative Examples 1 and 2. At the same time, the tensile strength of the materials in Examples 1-4 is ≥15 MPa, and the elongation at break is ≥400%, showing good toughness and strength.

[0043] Table 2 Foaming ratio of TPU foamed wire at different temperatures (diameter 0.6 mm nozzle, layer height 0.4 mm)

[0044] Temperature 180℃ 190℃ 200℃ 210℃ 220℃ 230℃ Comparative Example 2 0 0 0 0 0 0 Example 1 1.8 2.2 2.5 2.8 3.2 3.6 Example 2 2.1 2.4 2.6 3.1 3.4 3.8 Example 3 2.3 2.5 2.7 3.2 3.5 3.6 Example 4 2.2 2.3 2.5 2.7 3.1 3.3

[0045] From Table 2, the foaming TPU materials of Examples 1-4 can have a foaming ratio of 1.8 to 3.8 at 180-230°C, and the foaming ratio can be controlled at different temperatures.

[0046] Table 3: Different layer height printing test of Example 1 TPU foamed wire (diameter 0.8 mm nozzle)

[0047]

[0048] Note: "√" means that it can be normally printed by the FDM type 3D printer.

[0049] From Table 3, the TPU material prepared in Example 1 can be stably printed under different printing temperatures and different layer heights. This high controllability and stability make it have a significant process advantage in the field of 3D printing, and can meet the requirements of different application scenarios for material performance and printing accuracy.

[0050] The survival rate of cultured SD mouse preosteoblast cells (MC3T3-E1) on the surface of the TPU materials prepared in Examples 1-4 and Comparative Examples 1-2 was determined by MTT method (3-(4,5-dimethylthiazole-2)-2,5-diphenyl tetrazolium bromide, trade name: thiazole blue). First, the sample was sterilized by ultraviolet light, then placed in a multi-well plate, inoculated in the multi-well plate at a cell density of 2x10 4 cells / cm 2 , 2 mL of complete culture medium was added to each well, a total of four groups were set up including a blank group, and placed in a 37°C, 5% CO2 incubator for 24 h, the liquid was changed every other day, and after three weeks of culture, it was taken out. A zero setting group was set up, i.e. six wells of the experimental plate without cultured cells were selected and complete culture medium was added. 20 μL of MTT was added to each liquid-containing well at a time, and then incubated for 4 h, the liquid in each well was aspirated, rinsed with PBS buffer, and 150 μL of dimethyl sulfoxide was added to each well. After shaking for 10 min, the optical density (OD) value of each well was determined at 490 nm wavelength by enzyme-linked immunoassay instrument, and the relative cell survival rate was calculated according to formula (1). The test results are shown in Table 4. Figure 1

[0051]

[0052] From Figure 1 ​It can be concluded that the TPU materials prepared in Examples 1-4 have high cell survival rate and good growth state after co-cultured with MC3T3-E1 cells for 48 hours, indicating that the material surface can promote cell adhesion and proliferation. This good biocompatibility combined with the air permeability and porosity of the foamed structure makes the foamed TPU material have great application potential in the biomedical field, such as being used to manufacture tissue engineering scaffolds, drug release carriers, etc. The controllability of the foaming ratio can further optimize the pore structure of the material to meet the needs of different biomedical applications.

Claims

1. A method for preparing a 3D-printed controllable foamed TPU material, characterized in that, Includes the following steps: TPU, TPU surface modifier, foaming agent and alcohol fluid are mixed and then melt-extruded, cooled, formed into strips and wound up to obtain 3D printed controllable foamed TPU material; wherein, the alcohol fluid is one or a mixture of polyethylene glycol, polypropylene glycol, glycerol, ethylene glycol, 1,2-propanediol, sorbitol and 1,4-butanediol.

2. The method for preparing 3D-printed controllable foamed TPU material according to claim 1, characterized in that, The amount of alcohol fluid used is 1 to 2% of the TPU mass.

3. The method for preparing 3D-printed controllable foamed TPU material according to claim 1, characterized in that, The foaming agent is azodicarbonamide or sodium bicarbonate.

4. The method for preparing 3D-printed controllable foamed TPU material according to claim 1, characterized in that, The temperature of the melt extrusion is 150–220°C.

5. A 3D-printable controllable foaming TPU material prepared by the preparation method according to any one of claims 1 to 4.

6. The 3D-printable controllable foaming TPU material according to claim 5, characterized in that, The foaming temperature of the TPU material is 170–220°C.

7. The 3D-printable controllable foaming TPU material according to claim 5, characterized in that, The expansion ratio of the TPU material is 1 to 5 times.

8. The 3D-printable controllable foaming TPU material according to claim 5, characterized in that, The density of the TPU material is 0.5–0.9 g / cm³. 3 Tensile strength ≥15MPa, elongation at break ≥400%.

9. The application of the TPU material according to any one of claims 5 to 8 in 3D printing.

10. The application according to claim 9, characterized in that, The application method is as follows: the TPU material is used in a fused deposition modeling 3D printer at a printing temperature of 180℃~240℃ and a printing speed of 60~200mm / s.

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