A method for on-demand construction of mechanically anisotropic articles based on FDM technology

Abstract

The application discloses a method for constructing mechanical anisotropic products on demand based on FDM technology, and the method comprises the following steps: S1, printing a self-healing polyurethane material by using a fused deposition modeling printer, and the filling rate is 20-100%, so as to obtain a 3D printed product; and S2, performing heat treatment on the 3D printed product. The application realizes the precise regulation of the mechanical anisotropy of the 3D printed product in all directions, so that the anisotropy meets the preset requirement. The method is simple and efficient, solves the problem of the undesired anisotropy in the process of constructing the printed product by using the FDM technology in the prior art, and effectively widens the application of the FDM technology in the new functional field.

Description

Technical Field

[0001] This invention relates to the field of 3D printing, and more specifically, to a method for on-demand construction of anisotropic mechanical articles based on FDM technology. Background Technology

[0002] Anisotropy refers to the orientational dependence of a material's mechanical, electrical, thermal, or optical properties. In recent years, anisotropic materials have attracted widespread research interest in aerospace, sensing, soft robotics, and tissue engineering due to their high efficiency in material utilization and specific functional modification. Currently, the construction of anisotropic materials mainly achieves differences in mechanical or physical properties in specific directions by configuring structures or components in different orientations. However, the solid-state nature of anisotropic materials inevitably limits and constrains their manufacturing using traditional processes. In contrast, 3D printing technology, with its layer-by-layer accumulation molding method, can easily achieve flexible spatial configuration of the structure or components of three-dimensional objects. Against this backdrop, introducing 3D printing technology into the construction of anisotropic materials will provide virtually unlimited freedom for their design and manufacturing.

[0003] Fused deposition modeling (FDM) has become one of the most widely used 3D printing technologies due to its ease of operation and low cost. Existing strategies for constructing anisotropic objects using FDM technology mainly include shear-induced orientation, continuous fiber orientation, and gradient structure or material configuration. However, due to inherent technical limitations of FDM, unwanted anisotropy often results in the fabrication of anisotropic objects. Therefore, developing a method capable of on-demand fabrication of mechanically anisotropic products is of significant research importance. Summary of the Invention

[0004] To address the problems in existing technologies, this invention provides a method for on-demand construction of mechanically anisotropic articles based on FDM technology. On one hand, it pre-regulates the initial anisotropy of the FDM-printed article by setting the infill rate during the printing process. On the other hand, it controls the heat treatment temperature and time of the three-dimensional object after FDM printing. These two aspects work synergistically to effectively control the mechanical anisotropy of the 3D-printed article in all directions, ensuring that its anisotropy meets preset requirements. This solves the problem of unwanted anisotropy occurring during the construction of printed articles using existing FDM technology.

[0005] A method for on-demand fabrication of anisotropic mechanical articles based on FDM technology, the method comprising:

[0006] S1: Self-healing polyurethane material is printed using a fused deposition modeling printer with an infill rate of 20-100% to obtain 3D printed products;

[0007] S2: The 3D printed product is subjected to heat treatment at a temperature of 40-100°C for 5-60 minutes.

[0008] Preferably, the filling rate is 50-80%; the heat treatment temperature is 60-100℃, and the heat treatment time is 10-40 min.

[0009] In a preferred embodiment of the present invention, the polyurethane material is prepared from diisocyanate, macromolecular diol, small molecule chain extender, and catalyst; the molar ratio of the diisocyanate, macromolecular diol, small molecule chain extender, and catalyst is 100:15-30:60-85:0.1-1. Preferably, the molar ratio of the diisocyanate, macromolecular diol, small molecule chain extender containing diol or small molecule chain extender containing diamine, and catalyst is 100:20-30:75-80:0.4-0.8. Those skilled in the art can select a suitable molar ratio of the diisocyanate, macromolecular diol, small molecule chain extender, and catalyst according to actual needs. The small molecule chain extender is either a small molecule chain extender containing diol or a small molecule chain extender containing diamine. The small molecule chain extender reacts with the diisocyanate, thereby introducing dynamic bonds into the polyurethane material and endowing the polyurethane with self-healing properties.

[0010] Furthermore, the diisocyanate is one or more selected from isoflurane diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, terephthalic diisocyanate, 1,5-naphthalene diisocyanate, trimethylhexamethylene diisocyanate, and dicyclohexylmethane diisocyanate. The macromolecular diol is one or more selected from hydroxyl-terminated polyester diol, hydroxyl-terminated polyether diol, hydroxyl-terminated polybutadiene, and polysiloxane diol. The catalyst is one or more selected from dibutyltin dilaurate, triphenylbismuth, and triphenyltin chloride. Technical personnel can select appropriate diisocyanates, macromolecular diols, small molecule chain extenders, and catalysts according to actual needs to meet different performance requirements of polyurethane materials, such as mechanical strength, toughness, rheological properties, and glass transition temperature.

[0011] Furthermore, the hydroxyl-terminated polyester diol is one or more of poly(adipate diol), polycarbonate diol, and polycaprolactone diol; or the hydroxyl-terminated polyether diol is polytetramethylene ether diol and / or polypropylene oxide ether diol. The diamine-containing small-molecule chain extender is a hindered secondary amine diamine chain extender, preferably N,N′-diisopropylethylenediamine and / or N,N′-di-tert-butylethylenediamine; or the diol-containing small-molecule chain extender is an oxime-type dihydroxy chain extender. The oxime-type dihydroxy chain extender is preferably dimethylglyoxime and / or p-benzoquinone dioxime.

[0012] In another specific embodiment of the present invention, the polyurethane material is prepared by the following method:

[0013] 1) Heating the macromolecular diol removes the water content from the macromolecular diol to obtain the first intermediate product;

[0014] 2) Cool the first intermediate product, add the diisocyanate to it, react, and obtain an isocyanate-terminated polyurethane prepolymer;

[0015] 3) The small molecule chain extender and the catalyst are added to the isocyanate-terminated polyurethane prepolymer and heated to react, thereby obtaining the second intermediate product;

[0016] 4) The second intermediate product is cast into a mold and vacuum cured to obtain a self-healing polyurethane material.

[0017] The following solutions can be adopted:

[0018] 1) The macromolecular diol is added to a device equipped with a reflux condenser and stirred for 2 hours under vacuum at 120°C to completely remove the water contained in the macromolecular diol, which is the first intermediate product.

[0019] 2) The first intermediate product is cooled to a certain temperature, and the diisocyanate is added to the first intermediate product under a nitrogen atmosphere. The mixture is stirred, and after reacting for a period of time, an isocyanate-terminated polyurethane prepolymer is obtained.

[0020] 3) Under a nitrogen atmosphere, the small molecule chain extender and the catalyst are added to the isocyanate-terminated polyurethane prepolymer in step 2), heated to a certain temperature, stirred, and the second intermediate product is obtained after the viscosity of the reaction system increases to the point where it is about to climb the rod.

[0021] 4) The second intermediate product is cast into a polytetrafluoroethylene (PTFE) mold and cured in a vacuum oven to obtain a self-healing polyurethane material.

[0022] Furthermore, in step 1), the reaction temperature is 105–120℃, and the reaction time is 1.5–2 hours; in step 2), the reaction temperature is 60–80℃, and the reaction time is 1–2 hours; in step 3), the reaction temperature is 60–80℃, and the reaction time is 1–3 hours; in step 4), the vacuum curing temperature is 80–100℃, and the vacuum curing time is 8–12 hours. Technicians can select appropriate reaction times, vacuum curing times, and vacuum curing temperatures according to actual needs.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention uses macromolecular diols, diisocyanates, and small-molecule chain extenders containing diols or diamines as raw materials to design and synthesize a self-healing polyurethane material. This material is then printed using a fused deposition modeling (FDM) printer. On one hand, the initial anisotropy of the FDM-printed product is pre-controlled by setting the infill rate during the printing process. On the other hand, the interlayer bonding strength of the 3D object is effectively controlled by adjusting the heat treatment temperature and time after FDM printing. These two aspects work synergistically to achieve precise control of the mechanical anisotropy of the 3D-printed product in all directions, ensuring that the anisotropy meets preset requirements. This method is simple and efficient, solving the problem of unwanted anisotropy during the construction of printed products using existing FDM technology, and effectively broadening the application of FDM technology in novel functional fields. Furthermore, the polyurethane material of this invention possesses self-healing properties, endowing FDM-printed products with self-repair capabilities and extending their service life. Attached Figure Description

[0025] Figure 1 The tensile strength of the polyurethane material prepared in Example 1 of the present invention, after being heat-treated at 80°C for different times using FDM printing, is measured along the X-axis, Y-axis and Z-axis directions.

[0026] Figure 2 The mechanical orientations of the polyurethane material prepared in Example 1 of this invention, after being heat-treated at 80°C for different times using FDM printing, are compared with the X-axis direction in the Y-axis and Z-axis directions.

[0027] Figure 3 The tensile strength of the polyurethane material prepared in Example 2 of the present invention, after being heat-treated at 80°C for different times using FDM printing, is measured along the X-axis, Y-axis and Z-axis directions.

[0028] Figure 4 The mechanical orientations of the polyurethane material prepared in Example 2 of this invention, after being heat-treated at 80°C for different times using FDM printing, are compared between the Y-axis and Z-axis directions and the X-axis direction.

[0029] Figure 5 The tensile strength of the polyurethane material prepared in Example 3 of the present invention, after being heat-treated at 100°C for different times using FDM printing, is measured along the X-axis, Y-axis and Z-axis directions.

[0030] Figure 6 The mechanical anisotropy of the polyurethane material prepared in Example 3 of this invention, after being heat-treated at 100°C for different times using FDM printing, is shown in the Y-axis and Z-axis directions relative to the X-axis direction. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0032] Example 1

[0033] Preparation of polyurethane materials for on-demand fabrication of mechanically anisotropic articles based on FDM technology: 0.0175 mol of polycarbonate diol (number average molecular weight approximately 2000) was added to a three-necked flask equipped with a mechanical stirrer and stirred under vacuum at 120°C for 2 hours to completely remove residual moisture from the polycarbonate diol. Then, the reaction system was cooled to 50°C, and 0.0951 mol of diphenylmethane diisocyanate was added under a nitrogen atmosphere. The temperature was slowly increased to 70°C and reacted for 2 hours to obtain a polyurethane prepolymer. Then, 0.0776 mol N,N′-diisopropylethylenediamine and 0.0004 mol dibutyltin dilaurate catalyst were added to the above polyurethane prepolymer and reacted at 70°C for 1.5 h. When the viscosity of the reaction system reached a certain level, the reactants were cast into a polytetrafluoroethylene (PTFE) mold and cured in a vacuum oven at 100°C for 10 h to finally obtain a 3D printed polyurethane material with self-healing properties.

[0034] A method for on-demand construction of anisotropic mechanical products based on FDM technology: The aforementioned self-healing 3D printing polyurethane material is used to print samples using an FDM (Fused Deposition Modeling) printer to obtain printed products. The printing temperature is 185℃, the printing speed is 10mm / s, the printing platform temperature is 40℃, and the fill ratio is 100%.

[0035] Example 2

[0036] Preparation of polyurethane materials for on-demand fabrication of mechanically anisotropic products based on FDM technology: 0.0175 mol of polycaprolactone diol (number average molecular weight approximately 2000) was added to a three-necked flask equipped with a mechanical stirrer and stirred under vacuum at 120°C for 2 hours to completely remove residual moisture from the polycaprolactone diol. Then, the reaction system was cooled to 70°C, and 0.0963 mol of isoflurane diisocyanate was added under a nitrogen atmosphere. The temperature was slowly increased to 80°C and reacted for 2 hours to obtain a polyurethane prepolymer. Then, 0.0788 mol N,N′-di-tert-butylethylenediamine and 0.0005 mol dibutyltin dilaurate catalyst were added to the above polyurethane prepolymer and reacted at 80°C for 1.5 h. When the viscosity of the reaction system reached a certain level, the reactants were cast into a polytetrafluoroethylene (PTFE) mold and cured in a vacuum oven at 100°C for 10 h to finally obtain a 3D printed polyurethane material with self-healing properties.

[0037] A method for on-demand construction of anisotropic mechanical products based on FDM technology: The aforementioned self-healing 3D printing polyurethane material is used to print samples using an FDM (Fused Deposition Modeling) printer to obtain printed products. The printing temperature is 175℃, the printing speed is 10mm / s, the printing platform temperature is 60℃, and the fill ratio is 100%.

[0038] Example 3

[0039] Preparation of polyurethane materials for on-demand fabrication of mechanically anisotropic products based on FDM technology: 0.0315 mol of polytetramethylene ether glycol (number average molecular weight approximately 1000) was added to a three-necked flask equipped with a mechanical stirrer and stirred under vacuum at 120°C for 2 hours to completely remove residual moisture from the polytetramethylene ether glycol. Then, the reaction system was cooled to 60°C, and 0.1290 mol of hexamethylene diisocyanate was added under a nitrogen atmosphere. The temperature was slowly increased to 75°C and reacted for 2 hours to obtain a polyurethane prepolymer. Then, 0.0975 mol N,N′-di-tert-butylethylenediamine and 0.0004 mol dibutyltin dilaurate catalyst were added to the above polyurethane prepolymer and reacted at 80°C for 1.5 h. When the viscosity of the reaction system reached a certain level, the reactants were cast into a polytetrafluoroethylene (PTFE) mold and cured in a vacuum oven at 100°C for 10 h to finally obtain a 3D printed polyurethane material with self-healing properties.

[0040] A method for on-demand construction of anisotropic mechanical products based on FDM technology: The aforementioned self-healing 3D printing polyurethane material is printed using an FDM (Fused Deposition Modeling) printer to obtain the printed product. The printing temperature is 200℃, the printing speed is 10mm / s, the printing platform temperature is 50℃, and the fill ratio is 80%.

[0041] The self-healing efficiency, melting temperature, glass transition temperature, and tensile strength of the polyurethane materials prepared in Examples 1-3 were tested. The polyurethane materials prepared in Examples 1-3 were fabricated into dumbbell-shaped standard tensile specimens (70mm × 4mm × 2mm) for testing. In the self-healing experiment, a 1.5mm deep scratch was cut into the dumbbell-shaped standard tensile specimen (70mm × 4mm × 2mm) using a blade. The specimen was then repaired at 100℃ for 40 minutes, and the tensile strength of the repaired specimen was tested. The ratio of the tensile strength of the repaired specimen to that of the uncut specimen was defined as the self-healing efficiency. The melting temperature and glass transition temperature of the samples were measured using differential scanning calorimetry (DSC). The tensile strength of the dumbbell-shaped standard tensile specimen (70mm × 4mm × 2mm) was measured using a universal testing machine at a tensile rate of 100mm / s. The test results are shown in Table 1.

[0042] Table 1. Self-healing efficiency, melting temperature, glass transition temperature, and tensile strength of the self-healing 3D printing polyurethane materials prepared in Examples 1-3.

[0043] Self-healing efficiency (80℃) / % 89.7 94.5 90.5 Melting temperature / °C 170 150 180 Glass transition temperature / °C 4.6 -2.4 10.4 Tensile strength / MPa 32 28 33

[0044] Tensile tests were performed on the polyurethane materials prepared in Examples 1-3 and the products obtained by FDM printing to characterize their mechanical anisotropy. The test method was as follows: the samples printed in Examples 1 and 2 (thin sheets with the same thickness as the aforementioned dumbbell-shaped standard tensile specimens, also 2 mm thick) were treated at 80°C for 10 min, 20 min, and 30 min respectively. Finally, tensile tests were performed on the samples along different directions to characterize their mechanical anisotropy. The results are as follows: Figures 1-4 As shown. Among them, Figure 1 , Figure 3 The tensile strength of the polyurethane materials prepared in Examples 1 and 2, which were printed by FDM, along the X, Y, and Z axes after different heat treatment times at 80°C is shown respectively. Figure 2 , Figure 4The mechanical anisotropy of the polyurethane materials prepared in Examples 1 and 2, printed using FDM, compared to the X-axis, is shown after different heat treatment times at 80°C. Tensile tests were performed on the polyurethane materials prepared in Example 3, printed using FDM, to characterize their mechanical anisotropy. The test method was basically the same as described above, except that the samples were treated at 100°C. The results are as follows. Figure 5 and Figure 6 As shown.

[0045] Depend on Figure 1 and Figure 2 It can be seen that by controlling the heat treatment time of the FDM-printed product at 80℃, the anisotropy of the Y-axis mechanical strength relative to the X-axis mechanical strength can be controllably adjusted from 23.5% to 3.4%, and the anisotropy of the Z-axis mechanical strength relative to the X-axis mechanical strength can be controllably adjusted from 46.7% to 8.7%. Figure 3 and Figure 4 It can be seen that by controlling the heat treatment time of the FDM-printed product at 80℃, the anisotropy of the Y-axis mechanical strength relative to the X-axis can be controllably adjusted from 20.4% to 4.3%, and the anisotropy of the Z-axis mechanical strength relative to the X-axis can be controllably adjusted from 38.7% to 5.2%. Figure 5 and Figure 6 It can be seen that by controlling the heat treatment time of FDM printed products at 100℃, the anisotropy of the mechanical strength of the Y-axis relative to the mechanical strength of the X-axis can be controllably adjusted from 19.7% to 2.9%, and the anisotropy of the mechanical strength of the Z-axis relative to the mechanical strength of the X-axis can be controllably adjusted from 30.4% to 8.4%.

[0046] Compared to existing methods for constructing anisotropic materials based on FDM technology, such as shear-induced orientation, continuous fiber orientation, gradient structure, or material configuration, this invention controls the infill rate during printing and directly performs post-processing (controlling heat treatment temperature and time) on the finished product after printing. This allows for controllable adjustment of mechanical anisotropy. This method is simpler and more efficient, avoiding complex operation processes and providing a simple and efficient method for constructing mechanically anisotropic products.

[0047] In summary, this invention imparts self-healing properties to polyurethane materials by introducing dynamic bonds. Simultaneously, it utilizes this polyurethane material for FDM printing of three-dimensional objects. On one hand, the initial anisotropy of the FDM-printed product is pre-controlled by adjusting the infill rate during the printing process. On the other hand, the self-healing properties of the polyurethane material are activated by controlling the post-processing temperature and time of the three-dimensional object after FDM printing. These two aspects work synergistically to achieve precise control over the mechanical anisotropy of the FDM-printed product. Taking a heat treatment temperature of 80℃ as an example, the combination of infill rate control during printing and post-printing processing can achieve a mechanical anisotropy of 40%–100% in the FDM-printed product. This method for on-demand construction of mechanically anisotropic products based on FDM technology is simple, efficient, and has significant practical value.

Claims

1. A method for on-demand construction of anisotropic mechanical products based on FDM technology, characterized in that... The method includes: S1: Self-healing polyurethane material is printed using a fused deposition modeling printer with an infill rate of 50-80% to obtain 3D printed products; S2: The 3D printed product is subjected to heat treatment at a temperature of 60~100℃ for 10~40 minutes to obtain a 3D printed product with anisotropic size that meets the preset requirements.

2. The method according to claim 1, characterized in that: The polyurethane material is prepared from diisocyanate, macromolecular diol, small molecule chain extender, and catalyst; the molar ratio of diisocyanate, macromolecular diol, small molecule chain extender, and catalyst is 100:15~30:60~85:0.1~1; The small molecule chain extender is a small molecule chain extender containing diol or a small molecule chain extender containing diamine.

3. The method as described in claim 2, characterized in that: The molar ratio of the diisocyanate, macromolecular diol, small molecule chain extender, and catalyst is 100:20~30:75~80:0.4~0.

8.

4. The method as described in claim 2, characterized in that: The diisocyanate is one or more selected from isoflurone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, terephthalic diisocyanate, 1,5-naphthalene diisocyanate, trimethylhexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

5. The method as described in claim 2, characterized in that: The macromolecular diol is one or more of the following: hydroxyl-terminated polyester diol, hydroxyl-terminated polyether diol, hydroxyl-terminated polybutadiene, and polysiloxane diol.

6. The method as described in claim 5, characterized in that: The hydroxyl-terminated polyester diol is one or more of polyadipate diol, polycarbonate diol, and polycaprolactone diol. The hydroxyl-terminated polyether diol is polytetramethylene ether diol and / or polypropylene oxide ether diol.

7. The method as described in claim 2, characterized in that: The diamine-containing small molecule chain extender is a hindered secondary amine diamine chain extender; The diol-containing small molecule chain extender is an oxime-type dihydroxy chain extender.

8. The method as described in claim 7, characterized in that: The hindered secondary amine diamine chain extender is N,N′-diisopropylethylenediamine and / or N,N′-ditert-butylethylenediamine; The oxime dihydroxy chain extender is dimethylglyoxime and / or p-benzoquinone dioxime.

9. The method as described in claim 2, characterized in that: The catalyst is one or more of dibutyltin dilaurate, triphenylbismuth, and triphenyltin chloride.

10. The method as described in claim 2, characterized in that... The polyurethane material is prepared by the following method: 1) The macromolecular diol is heated to remove water, yielding the first intermediate product; 2) Cool the first intermediate product, add the diisocyanate to it, react, and obtain an isocyanate-terminated polyurethane prepolymer; 3) The small molecule chain extender and the catalyst are added to the isocyanate-terminated polyurethane prepolymer and heated to react, thereby obtaining the second intermediate product; 4) The second intermediate product is cast into a mold and vacuum cured to obtain a self-healing polyurethane material.

11. The method as described in claim 10, characterized in that: In step 1), the reaction temperature is 105~120℃, and the reaction time is 1.5~2h; and / or In step 2), the reaction temperature is 60~80℃, and the reaction time is 1~2h; and / or In step 3), the reaction temperature is 60~80℃, and the reaction time is 1~3h; and / or In step 4), the vacuum curing temperature is 80~100℃ and the vacuum curing time is 8~12h.

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