Method for constructing mechanical anisotropic product as required based on FDM technology

Abstract

The invention discloses a method for constructing a mechanical anisotropic product as required based on an FDM (fused deposition modeling) technology, and the method comprises the following steps: S1, printing a self-healing polyurethane material by adopting a fused deposition modeling printer at a filling rate of 20-100% to obtain a 3D printed product; and S2, the 3D printing product is subjected to heat treatment. The mechanical anisotropy of the 3D printing product in all directions is precisely regulated and controlled, the anisotropy meets the preset requirement, the method is simple, convenient and efficient, the problem that in the prior art, undesirable anisotropy occurs in the printing product construction process through the FDM technology is solved, and the application range of the FDM technology in the novel functional field is effectively widened.

Description

Technical Field

[0001] The present invention relates to the field of 3D printing, and more particularly to a method for constructing mechanically anisotropic products on demand based on FDM technology. Background Art

[0002] Anisotropy refers to the ability of a material to exhibit directional dependence in its mechanical, electrical, thermal or optical properties. In recent years, anisotropic materials have attracted extensive research interest in many fields such as aerospace, sensing, soft robotics and tissue engineering due to their high efficiency in material utilization and specific functional modification. At present, the construction of anisotropic materials is mainly achieved by configuring the structure or components in different directions to achieve differences in mechanical or physical properties in a specific direction. However, due to the solid characteristics of anisotropic materials, they are inevitably restricted and constrained in the manufacture using traditional manufacturing processes. In contrast, 3D printing technology can easily achieve flexible spatial configuration of the structure or components of three-dimensional objects because it adopts a layer-by-layer cumulative molding method. In this context, introducing 3D printing technology into the construction of anisotropic materials will provide unlimited freedom for the design and manufacture of anisotropic materials.

[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 anisotropy based on FDM technology mainly include shear-induced orientation, continuous fiber orientation, and gradient structure or material configuration. However, due to the inherent technical defects of FDM technology, it often leads to undesirable anisotropy in the process of constructing anisotropic objects. Therefore, it is of great research significance to develop a method that can realize the on-demand construction of mechanical anisotropic products. Summary of the invention

[0004] In order to solve the problems in the prior art, the present invention provides a method for constructing mechanical anisotropic products on demand based on FDM technology. On the one hand, the initial anisotropy size of the FDM printed product is pre-regulated by setting the filling rate during the printing process. On the other hand, the heat treatment temperature and heat treatment time of the three-dimensional object after FDM printing are controlled. The two aspects work together to effectively control the mechanical anisotropy size of the 3D printed product along all directions, so that its anisotropy size meets the preset requirements, thereby solving the problem of undesirable anisotropy in the process of constructing printed products using FDM technology in the prior art.

[0005] A method for constructing a mechanically anisotropic product on demand based on FDM technology, the method comprising:

[0006] S1: Printing the self-healing polyurethane material using a fused deposition modeling printer with a filling rate of 20 to 100% to obtain a 3D printed product;

[0007] S2: heat treating the 3D printed product at a temperature of 40 to 100° C. for 5 to 60 minutes.

[0008] Preferably, the filling rate is 50-80%; the heat treatment temperature is 60-100° C., 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, the macromolecular diol, the small molecule chain extender and the catalyst is 100:15-30:60-85:0.1-1. Preferably, the molar ratio of the diisocyanate, the macromolecular diol, the small molecule chain extender containing diol or the small molecule chain extender containing diamine and the catalyst is 100:20-30:75-80:0.4-0.8. The technician can select the appropriate molar ratio of the diisocyanate, the macromolecular diol, the small molecule chain extender and the catalyst according to actual needs. Among them, the small molecule chain extender is a small molecule chain extender containing diol or a small molecule chain extender containing diamine. The small molecule chain extender reacts with the diisocyanate to introduce dynamic bonds into the polyurethane material and give the polyurethane self-healing properties.

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

[0011] Furthermore, the terminal hydroxyl polyester diol is one or more of polyadipate small molecule diol ester diol, polycarbonate diol, and polycaprolactone diol; or the terminal hydroxyl 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 dihydroxy chain extender. The oxime 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 to remove water from the macromolecular diol to obtain a first intermediate product;

[0014] 2) cooling the first intermediate product, adding the diisocyanate thereto, reacting to obtain an isocyanate-terminated polyurethane prepolymer;

[0015] 3) adding the small molecule chain extender and the catalyst to the isocyanate-terminated polyurethane prepolymer, heating and reacting to obtain a second intermediate product;

[0016] 4) Casting the second intermediate product into a mold and vacuum curing it to obtain a self-healing polyurethane material.

[0017] The following solutions can be adopted:

[0018] 1) adding the macromolecular diol into a device equipped with condensation reflux, stirring for 2 hours under vacuum conditions at 120° C., thereby completely removing the water contained in the macromolecular diol, which is the first intermediate product;

[0019] 2) cooling the first intermediate product to a certain temperature, adding the diisocyanate to the first intermediate product under a nitrogen atmosphere, stirring, and reacting the two for a period of time to obtain an isocyanate-terminated polyurethane prepolymer.

[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 viscosity of the reaction system increases to a point where it is about to climb the pole, thereby obtaining a second intermediate product.

[0021] 4) Casting the second intermediate product into a polytetrafluoroethylene (PTFE) mold and curing it in a vacuum oven to obtain a self-healing polyurethane material.

[0022] Further, in step 1), the reaction temperature is 105-120°C, and the reaction time is 1.5-2h; in step 2), the reaction temperature is 60-80°C, and the reaction time is 1-2h; in step 3), the reaction temperature is 60-80°C, and the reaction time is 1-3h; in step 4), the vacuum curing temperature is 80-100°C, and the vacuum curing time is 8-12h. The technicians can select the appropriate reaction time, vacuum curing time, and vacuum curing temperature according to actual needs.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention adopts macromolecular diol, diisocyanate, small molecule chain extender containing diol or diamine as raw materials, designs and synthesizes self-healing polyurethane material, and prints it by fused deposition modeling printer, on the one hand, by setting the filling rate in the printing process to pre-regulate the initial anisotropy size of FDM printed products, on the other hand, by controlling the heat treatment temperature and heat treatment time of the three-dimensional object after FDM printing is completed, the interlayer bonding strength of the three-dimensional object is effectively controlled, and the two aspects work together to achieve the precise regulation of the mechanical anisotropy size of the 3D printed product in all directions, so that its anisotropy size meets the preset requirements, the method is simple and efficient, solves the problem of undesirable anisotropy in the process of FDM technology to construct printed products in the prior art, and effectively broadens the application of FDM technology in new functional fields. In addition, the polyurethane material of the present invention has self-healing properties, endows FDM printed products with self-repairing ability, and extends the service life of FDM printed products. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The tensile strength of the product obtained by FDM printing of the polyurethane material prepared in Example 1 of the present invention at different heat treatment times at 80° C. along the X-axis, Y-axis and Z-axis directions;

[0026] Figure 2 The mechanical directions of the samples in the Y-axis and Z-axis directions compared with the X-axis direction after the products obtained by FDM printing of the polyurethane material prepared in Example 1 of the present invention at 80° C. for different heat treatment times;

[0027] Figure 3 The tensile strength of the product obtained by FDM printing of the polyurethane material prepared in Example 2 of the present invention at different heat treatment times at 80° C. along the X-axis, Y-axis and Z-axis directions;

[0028] Figure 4 The mechanical directions of the samples in the Y-axis and Z-axis directions compared with the X-axis direction after the products obtained by FDM printing of the polyurethane material prepared in Example 2 of the present invention at 80° C. for different heat treatment times;

[0029] Figure 5 The tensile strength of the product obtained by FDM printing of the polyurethane material prepared in Example 3 of the present invention at 100° C. for different heat treatment times along the X-axis, Y-axis and Z-axis directions;

[0030] Figure 6 The mechanical dimensions of the product obtained by FDM printing of the polyurethane material prepared in Example 3 of the present invention in the Y-axis and Z-axis directions compared with the X-axis direction after heat treatment for different times at 100°C. DETAILED DESCRIPTION

[0031] The present invention is described in detail below in conjunction with specific drawings and embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0032] Example 1

[0033] Preparation of polyurethane material for on-demand construction of mechanically anisotropic products based on FDM technology: 0.0175 mol of polycarbonate diol (number average molecular weight of about 2000) was added to a three-necked flask equipped with a mechanical stirrer and stirred for 2 hours under vacuum conditions at 120°C to completely remove the water residue contained in 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, and the temperature was slowly raised to 70°C for reaction 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-mentioned polyurethane prepolymer and reacted at 70°C for 1.5 hours. When the viscosity of the reaction system reached a certain level, the reactant was cast into a polytetrafluoroethylene (PTFE) mold and cured in a vacuum oven at 100°C for 10 hours to finally obtain a 3D printing polyurethane material with self-healing properties.

[0034] A printing method for constructing mechanical anisotropic products on demand based on FDM technology: The 3D printing polyurethane material with self-healing properties prepared above is used to print and shape a sample using an FDM (fused deposition modeling) printer to obtain a printed product. The printing temperature is 185°C, the printing speed is 10mm / s, the printing platform temperature is 40°C, and the fill rate ratio is 100%.

[0035] Example 2

[0036] Preparation of polyurethane material for on-demand construction of mechanically anisotropic products based on FDM technology: 0.0175 mol of polycaprolactone diol (number average molecular weight of about 2000) was added to a three-necked flask equipped with a mechanical stirrer and stirred for 2 hours under vacuum conditions at 120°C to completely remove the water residue contained in the polycaprolactone diol. Then, the reaction system was cooled to 70°C, and 0.0963 mol of isophorone diisocyanate was added under a nitrogen atmosphere, and the temperature was slowly raised to 80°C for reaction 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-mentioned polyurethane prepolymer and reacted at 80°C for 1.5 hours. When the viscosity of the reaction system reached a certain level, the reactant was cast into a polytetrafluoroethylene (PTFE) mold and cured in a vacuum oven at 100°C for 10 hours to finally obtain a 3D printing polyurethane material with self-healing properties.

[0037] A printing method for constructing mechanical anisotropic products on demand based on FDM technology: The 3D printing polyurethane material with self-healing properties prepared above is used to print and shape a sample using an FDM (fused deposition modeling) printer to obtain a printed product. The printing temperature is 175°C, the printing speed is 10 mm / s, the printing platform temperature is 60°C, and the fill rate ratio is 100%.

[0038] Example 3

[0039] Preparation of polyurethane material for on-demand construction of mechanical anisotropic products based on FDM technology: 0.0315 mol of polytetramethylene ether glycol (number average molecular weight of about 1000) was added to a three-necked flask equipped with a mechanical stirrer and stirred for 2 hours under vacuum conditions at 120°C to completely remove the water residue contained in 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, and the temperature was slowly raised to 75°C for reaction 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-mentioned polyurethane prepolymer and reacted at 80°C for 1.5 hours. When the viscosity of the reaction system reached a certain level, the reactant was cast into a polytetrafluoroethylene (PTFE) mold and cured in a vacuum oven at 100°C for 10 hours to finally obtain a 3D printing polyurethane material with self-healing properties.

[0040] A printing method for constructing mechanical anisotropic products on demand based on FDM technology: The 3D printing polyurethane material with self-healing properties prepared above is used to print and shape a sample using an FDM (fused deposition modeling) printer to obtain a printed product. The printing temperature is 200°C, the printing speed is 10mm / s, the printing platform temperature is 50°C, and the fill rate ratio is 80%.

[0041] The self-healing efficiency, melting temperature, glass transition temperature and tensile strength of the polyurethane materials prepared in Examples 1 to 3 were tested. The polyurethane materials prepared in Examples 1 to 3 were made into dumbbell-shaped standard tensile specimens (70mm×4mm×2mm) and then tested. Among them, the self-healing experiment was to use a blade to cut a scratch with a depth of about 1.5mm on the dumbbell-shaped standard tensile specimen (70mm×4mm×2mm), and then repair the sample at 100°C for 40 minutes, and then test the tensile strength of the repaired sample, and the ratio of the tensile strength of the repaired sample to the tensile strength of the uncut sample was defined as the self-healing efficiency. The melting temperature and glass transition temperature of the sample were tested by differential scanning calorimetry (DSC). The tensile strength of the dumbbell-shaped standard tensile specimen (70mm×4mm×2mm) was tested by a universal testing machine at a tensile rate of 100mm / s. The test results are shown in Table 1

[0042] Table 1 Self-repairing efficiency, melting temperature, glass transition temperature and tensile strength of 3D printing polyurethane materials with self-repairing properties prepared in Examples 1 to 3

[0043] Example 1 Example 2 Example 3 Self-repair efficiency (80℃) / % 89.7 94.5 90.5 Melting temperature / ℃ 170 150 180 Glass transition temperature / ℃ 4.6 -2.4 10.4 Tensile strength / MPa 32 28 33

[0044] The products obtained by FDM printing of the polyurethane materials prepared in Examples 1 to 3 were subjected to tensile tests to characterize their mechanical anisotropy. The test method is: the samples printed in Examples 1 and 2 (thin sheets with the same thickness as the aforementioned dumbbell-shaped standard tensile specimens, whose thickness is also 2 mm) are treated at 80°C for 10 minutes, 20 minutes, and 30 minutes respectively, and finally the samples are subjected to tensile tests in different directions to characterize their mechanical anisotropy. The results are as follows: Figures 1 to 4 As shown. Among them, Figure 1 , Figure 3 The tensile strengths of the products of the polyurethane materials prepared in Example 1 and Example 2 printed by FDM after different heat treatment times at 80°C along the X-axis, Y-axis and Z-axis directions are respectively shown; Figure 2 , Figure 4The mechanical anisotropy of the polyurethane material obtained by FDM printing in Example 1 and Example 2 in the Y-axis and Z-axis directions relative to the X-axis direction after different heat treatment times at 80°C is shown. The product obtained by FDM printing of the polyurethane material obtained by Example 3 was subjected to a tensile test to characterize its mechanical anisotropy. The test method is basically the same as the above, except that the sample is treated at 100°C. The results are shown in Figure 5 and Figure 6 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°C, the anisotropy of the Y-axis mechanical strength relative to the X-axis mechanical strength can be controlled from 23.5% to 3.4%, and the anisotropy of the Z-axis mechanical strength relative to the X-axis mechanical strength can be controlled 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°C, the anisotropy of the Y-axis mechanical strength relative to the X-axis mechanical strength can be controlled from 20.4% to 4.3%, and the anisotropy of the Z-axis mechanical strength relative to the X-axis mechanical strength can be controlled from 38.7% to 5.2%. Figure 5 and Figure 6 It can be seen that by controlling the heat treatment time of the FDM-printed products at 100°C, the anisotropy of the Y-axis mechanical strength relative to the X-axis mechanical strength can be controlled from 19.7% to 2.9%, and the anisotropy of the Z-axis mechanical strength relative to the X-axis mechanical strength can be controlled from 30.4% to 8.4%.

[0046] Compared with the prior art methods of constructing anisotropy based on FDM technology, such as shear induced orientation, continuous fiber orientation, gradient structure or material configuration, the present invention controls the filling rate during the printing process and directly post-processes the product after printing (controls the heat treatment temperature and heat treatment time), which can achieve controllable adjustment of mechanical anisotropy. This method is simpler and more efficient, avoids complicated operation processes, and provides a simple and efficient method for constructing mechanical anisotropic products.

[0047] As described in the summary, the present invention introduces dynamic bonds into the polyurethane material to give the material self-healing properties, and uses the polyurethane material FDM to print three-dimensional objects. On the one hand, the initial anisotropy of the FDM printed product is pre-regulated by setting the filling rate during the printing process, and on the other hand, the self-healing properties of the polyurethane material are activated by controlling the post-processing temperature and post-processing time of the three-dimensional object after FDM printing. The two aspects work synergistically to achieve precise control of the mechanical anisotropy of the FDM printed product. Taking the heat treatment temperature of 80°C as an example, the combination of the control of the filling rate during the printing process and the post-printing processing can achieve a mechanical anisotropy of the FDM printed product of 40 to 100%. The method of the present invention for constructing mechanical anisotropic products on demand based on FDM technology is simple and efficient, and has important practical value.

Claims

1. A method for constructing mechanical anisotropic products on demand based on FDM technology, characterized in that The method comprises: S1: Printing the self-healing polyurethane material using a fused deposition modeling printer with a filling rate of 20 to 100% to obtain a 3D printed product; S2: heat treating the 3D printed product at a temperature of 40 to 100° C. for 5 to 60 minutes.

2. The method according to claim 1, characterized in that: The filling rate is 50-80%; and / or The heat treatment temperature is 60-100° C., and the heat treatment time is 10-40 minutes.

3. 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； Wherein, the small molecule chain extender is a small molecule chain extender containing diol or a small molecule chain extender containing diamine.

4. The method according to claim 3, characterized in that: The molar ratio of the diisocyanate, the macromolecular diol, the small molecular chain extender and the catalyst is 100:20-30:75-80:0.4-0.

8.

5. The method according to claim 3, characterized in that: The diisocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, p-phenylene diisocyanate, 1,5-naphthalene diisocyanate, trimethylhexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

6. The method according to claim 3, characterized in that: The macromolecular diol is one or more of hydroxyl-terminated polyester diol, hydroxyl-terminated polyether diol, hydroxyl-terminated polybutadiene, and polysiloxane diol; Preferably, The hydroxyl-terminated polyester diol is one or more of polyadipate small molecule diol ester diol, polycarbonate diol, and polycaprolactone diol; The hydroxyl-terminated polyether diol is polytetramethylene ether diol and / or polypropylene oxide ether diol.

7. The method according to claim 3, 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 dihydroxy chain extender; Preferably, The hindered secondary amine diamine chain extender is N,N′-diisopropylethylenediamine and / or N,N′-di-tert-butylethylenediamine; The oxime dihydroxy chain extender is diacetyl oxime and / or p-benzoquinone dioxime.

8. The method according to claim 3, characterized in that: The catalyst is one or more of dibutyltin dilaurate, triphenylbismuth and triphenyltin chloride.

9. The method according to claim 3, characterized in that The polyurethane material is prepared by the following method: 1) heating the macromolecular diol to remove water to obtain a first intermediate product; 2) cooling the first intermediate product, adding the diisocyanate thereto, reacting to obtain an isocyanate-terminated polyurethane prepolymer; 3) adding the small molecule chain extender and the catalyst to the isocyanate-terminated polyurethane prepolymer, heating and reacting to obtain a second intermediate product; 4) Casting the second intermediate product into a mold and vacuum curing it to obtain a self-healing polyurethane material.

10. The method according to claim 9, characterized in that: In step 1), the reaction temperature is 105-120°C and the reaction time is 1.5-2h; and / or In step 2), the reaction temperature is 60-80°C and the reaction time is 1-2h; and / or In step 3), the reaction temperature is 60-80°C and the reaction time is 1-3h; and / or In step 4), the vacuum curing temperature is 80-100° C., and the vacuum curing time is 8-12 hours.

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