Self-repairing shape memory polyurethane material as well as preparation method and 4D (four-dimensional) printing method thereof

Abstract

The invention provides a self-repairing shape memory polyurethane material. The self-repairing shape memory polyurethane material is prepared from diisocyanate, macromolecular dihydric alcohol, benzil dioxime and a catalyst in a molar ratio of 100: (15-40): (60-80): (0.1-2). The glass transition temperature of the polyurethane material is controlled by controlling the feeding ratio and types of macromolecular dihydric alcohol and diisocyanate, so that the shape memory behavior of the polyurethane material at different temperatures is realized; the glass-transition temperature and the self-healing efficiency of the benzil dioxime are controlled by controlling the feed ratio of the benzil dioxime, and the self-repairing performance and multiple structure variability of the benzil dioxime can meet the diversified and personalized requirements of 4D printing. The overall structure is divided into a plurality of small structures, printing of the small structures is completed by selecting polyurethane materials with different shape memories, assembling of the overall structure is completed by means of the self-repairing performance of the polyurethane materials, different shape memory response temperatures of different parts of the overall structure are achieved, and then multiple responses of a 4D printing object are achieved.

Description

Technical Field

[0001] The present invention relates to the field of 4D printing, and more particularly to a self-repairing shape memory polyurethane material and a preparation method thereof and a 4D printing method. Background Art

[0002] 4D printing is the introduction of the fourth dimension "time" into 3D printing, which is used to describe the integration of 3D printing and smart materials, so that 3D printed objects can change their shape, properties or functions under external stimuli (such as heat, light, water or pH, etc.). Due to the inherent properties of 4D printing, it has attracted widespread research interest in the fields of sensors, actuators, robots, medicine and intelligent systems in recent years. Smart materials mainly include shape memory materials and self-healing materials. Self-healing materials refer to the ability of materials to recover from physical damage under external stimuli. Introducing self-healing materials into 4D printing, thereby giving 4D printed objects the ability to self-repair damage, will help to extend the service life of 4D printed objects and expand the applicability of 4D printed objects in various complex application scenarios.

[0003] Shape memory polymer (SMP) is currently one of the most widely used smart materials in the field of 4D printing due to its advantages such as large deformation, fast response speed and diverse driving modes. However, since existing shape memory polymers can usually only achieve one or two structural changes, the current 4D printed objects based on shape memory polymers can only complete simple structural deformations, and there are still great limitations for some 4D printed objects with diverse structural changes and large personalized needs. In addition, the current lack of 3D printable smart materials also limits the development of 4D printing technology. Therefore, in view of the shortcomings of existing 4D printing, it is of great research significance to develop a new type of smart material that can meet the diverse and personalized needs of 4D printing. Summary of the invention

[0004] In order to solve the problems in the prior art, the present invention provides a self-healing shape memory polyurethane material. First, by reacting benzil dioxime with diisocyanate to generate oxime-urethane bonds, dynamic bonds are introduced into the polyurethane material, and the polyurethane is endowed with self-healing properties; secondly, by controlling the feed ratio and type of macromolecular diols and diisocyanates, the glass transition temperature of the polyurethane material is controlled, thereby achieving its shape memory behavior at different temperatures; finally, by controlling the feed ratio of benzil dioxime, the glass transition temperature and self-healing efficiency of the polyurethane material are controlled. This new intelligent material is applied to 4D printing, and its self-healing properties and multiple variable structures can meet the diversified and personalized needs of 4D printing.

[0005] One of the purposes of the present invention is to provide a self-healing shape memory polyurethane material, wherein the polyurethane material is prepared from diisocyanate, macromolecular diol, benzil dioxime and a catalyst; the molar ratio of the diisocyanate, the macromolecular diol, the benzil dioxime and the catalyst is 100:15-40:60-80:0.1-2. Preferably, the molar ratio of the diisocyanate, the macromolecular diol, the benzil dioxime and the catalyst is 100:15-20:70-80:0.5-1. The technician can select a suitable molar ratio of the diisocyanate, the macromolecular diol, the benzil dioxime and the catalyst according to the actual 4D printing requirements, i.e., the glass transition temperature requirements and the self-healing efficiency requirements.

[0006] In one preferred embodiment of the present invention, 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. Preferably, the hydroxyl-terminated polyester diol is one or more of polyadipate small molecule diol ester diol, polycarbonate diol, and polycaprolactone diol; or the hydroxyl-terminated polyether diol is polytetramethylene ether diol and / or polypropylene oxide ether diol. The technicians can select the appropriate types of the diisocyanate, the macromolecular diol, and the catalyst according to the actual 4D printing requirements, namely the glass transition temperature requirements and the self-healing efficiency requirements.

[0007] The second object of the present invention is to provide a method for preparing a self-repairing shape memory polyurethane material according to one of the objects of the present invention, the method comprising:

[0008] S1: heating the macromolecular diol to remove water from the macromolecular diol to obtain a first intermediate product;

[0009] S2: cooling the first intermediate product, and adding the diisocyanate thereto to obtain an isocyanate-terminated polyurethane prepolymer;

[0010] S3: adding the benzildioxime and the catalyst to the isocyanate-terminated polyurethane prepolymer, heating and reacting to obtain a second intermediate product;

[0011] S4: Casting the second intermediate product into a mold, and vacuum curing to obtain a self-repairing shape memory polyurethane material.

[0012] The following solutions can be adopted:

[0013] 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;

[0014] 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;

[0015] 3) under a nitrogen atmosphere, adding benzildioxime and a catalyst to the isocyanate-terminated polyurethane prepolymer in step 2), heating to a certain temperature, stirring, and obtaining a second intermediate product after the viscosity of the reaction system increases to a point where it is about to climb the pole;

[0016] 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.

[0017] In one preferred embodiment of the present invention, in step S1, the reaction temperature is 105-120°C, and the reaction time is 1.5-2h; in step S2, the reaction temperature is 60-80°C, and the reaction time is 1-2h; in step S3, the reaction temperature is 60-80°C, and the reaction time is 1-3h; in step S4, the vacuum curing temperature is 80-100°C, and the vacuum curing time is 8-12h. The technician can select the appropriate reaction time, vacuum curing time, and vacuum curing temperature according to actual needs.

[0018] The third object of the present invention is to provide a 4D printing method for the self-repairing shape memory polyurethane material of the first object of the present invention or the self-repairing shape memory polyurethane material prepared by the method of the second object of the present invention, characterized in that:

[0019] 1) splitting the whole structure to be printed and slicing it using a fused deposition modeling printer to obtain sliced ​​parts;

[0020] 2) using the self-repairing shape memory polyurethane material with different response temperatures to print the sliced ​​parts respectively, heating them, and assembling them to obtain the overall structure A;

[0021] 3) heating the overall structure A to obtain an overall structure B assembled from the split parts;

[0022] 4) cooling the overall structure B;

[0023] 5) The overall structure B is subjected to a heating treatment to reach the temperature response threshold of each of the split parts in turn, and the split parts are restored and assembled into the overall structure A in turn.

[0024] During the 4D printing process, the self-healing properties of polyurethane materials with different response temperatures are used to assemble the small structures printed separately into an overall structure. At the same time, the different response temperatures of the split parts to shape memory are used to achieve multiple responses of the overall structure.

[0025] The following solutions can be adopted:

[0026] 1) The overall structure to be printed is split into several small structures, and then several of the split small structures are sliced ​​using printing software based on fused deposition modeling (FDM) to obtain several slice parts.

[0027] 2) Select polyurethane materials with different shape memory response temperatures, use FDM to print several slice parts, heat them after printing, and assemble them together to obtain the overall structure A.

[0028] 3) heating the overall structure A, and obtaining an overall structure B assembled from the split parts after a period of time, and pre-programming the split parts into different temporary shapes;

[0029] 4) Cooling down the overall structure B to fix the temporary shape;

[0030] 5) The overall structure B is heated. Since the response temperatures of the split parts to shape memory are different, the temperature response thresholds of the split parts are reached in turn during the heating process, and the split parts are restored in turn, thereby achieving multiple responses of the overall structure. As the temperature rises to a temperature higher than the split part with the highest glass transition temperature, the split parts are restored and can be assembled into the overall structure A.

[0031] In one preferred embodiment of the present invention, in step 3), the temperature is higher than the temperature response threshold of each split part; in step 4), the temperature is lower than the temperature response threshold of each split part. In the present invention, the temperature response threshold specifically refers to the glass transition temperature of each split part.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention uses macromolecular diols, diisocyanates, benzil dioxime, and catalysts as raw materials, designs and synthesizes a new functional polyurethane material with self-healing properties and shape memory effect, and applies it to 4D printing. First, benzil dioxime reacts with diisocyanates to generate oxime-urethane bonds, introduces dynamic bonds into polyurethane materials, and gives polyurethane self-healing properties; secondly, by controlling the feed ratio and type of macromolecular diols and diisocyanates, the glass transition temperature of the polyurethane material is controlled, and then the shape memory behavior at different temperatures is realized; finally, by controlling the feed ratio of benzil dioxime, the glass transition temperature and self-healing efficiency of the polyurethane material are controlled. This new intelligent material is applied to 4D printing, and its self-healing properties and multiple variable structures can meet the diversified and personalized needs of 4D printing.

[0034] 2. The present invention divides the overall structure into multiple small structures, selects polyurethane materials with different shape memories to print each small structure separately, and finally uses the self-healing properties of the polyurethane materials to assemble the overall structure, thereby achieving different shape memory response temperatures of different parts of the overall structure, thereby achieving multiple responses of 4D printed objects, which will be beneficial to broadening the adaptability of 4D printed objects in various complex printing scenarios.

[0035] 3. The self-repairing shape memory polyurethane material of the present invention has self-repairing properties, which endows the 4D printed object with self-repairing ability, and is beneficial to prolonging the service life of the 4D printed object. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The overall structure and structural splitting scheme of the humanoid robot model in Example 1 of the present invention;

[0037] Figure 2 The structure of the B1 part after the humanoid robot model in Example 1 of the present invention is disassembled;

[0038] Figure 3 The structure of the B2 part after the humanoid robot model in Example 1 of the present invention is disassembled;

[0039] Figure 4 This is the B3 structure of the humanoid robot model after being disassembled in Example 1 of the present invention. DETAILED DESCRIPTION

[0040] 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.

[0041] Example 1

[0042] Since the present invention first needs to prepare self-healing shape memory polyurethane materials with different shape memory response temperatures, in order to better distinguish the prepared self-healing shape memory polyurethane materials, they are named TPU-SMP-X (wherein X is 1, 2, 3, 4...), and the glass transition temperature of the polyurethane material is adjusted by adjusting the hard segment content, so that the prepared polyurethane material has different self-healing response temperatures.

[0043] Preparation of self-repairing shape memory polyurethane materials:

[0044] (1) Preparation method of TPU-SMP-1 (hard segment content of 50%): 0.0175 mol of polytetramethylene ether glycol (number average molecular weight of 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 polycarbonate diol. Then, the reaction system was cooled to 60°C, and 0.0885 mol of diphenylmethane diisocyanate was added under a nitrogen atmosphere, and the temperature was slowly raised to 65°C for reaction for 2 hours to obtain a polyurethane prepolymer. Then, 0.0535 mol of benzildioxime and 0.0006 mol of dibutyltin dilaurate catalyst were added to the above-mentioned polyurethane prepolymer and reacted at 75°C for 2 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 obtain a self-healing shape memory polyurethane material TPU-SMP-1 with a hard segment content of 50%.

[0045] (2) Preparation of TPU-SMP-2 (hard segment content of 55%): 0.0315 mol of polytetramethylene ether glycol (number average molecular weight of 1000) was added to a three-necked flask equipped with a mechanical stirrer and stirred at 120°C under vacuum for 2 hours to completely remove the water residue contained in the polycarbonate diol. Then, the reaction system was cooled to 60°C, and 0.0939 mol of diphenylmethane diisocyanate was added under nitrogen atmosphere, and the temperature was slowly raised to 60°C for reaction for 2 hours to obtain a polyurethane prepolymer. Then, 0.0624 mol of benzildioxime and 0.0006 mol of dibutyltin dilaurate catalyst were added to the above-mentioned polyurethane prepolymer and reacted at 70°C for 2 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 obtain a self-healing shape memory polyurethane material TPU-SMP-2 with a hard segment content of 55%.

[0046] (3) Preparation method of TPU-SMP-3 (hard segment content of 60%): 0.0280 mol of polytetramethylene ether glycol (number average molecular weight of 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 polycarbonate diol. Then, the reaction system was cooled to 60°C, and 0.0993 mol of diphenylmethane diisocyanate was added under a nitrogen atmosphere, and the temperature was slowly raised to 60°C for reaction for 2 hours to obtain a polyurethane prepolymer. Then, 0.0713 mol of benzildioxime and 0.0003 mol of dibutyltin dilaurate catalyst were added to the above-mentioned polyurethane prepolymer and reacted at 65°C for 1 hour. 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 obtain a self-healing shape memory polyurethane material TPU-SMP-3 with a hard segment content of 60%.

[0047] The self-healing efficiency, melting temperature, glass transition temperature, shape memory response temperature, shape memory fixation rate and shape memory recovery rate of self-healing shape memory polyurethane materials TPU-SMP-1, TPU-SMP-2 and TPU-SMP-3 were tested. TPU-SMP-1, TPU-SMP-2 and TPU-SMP-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℃ for 40min, 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 effect. The melting temperature and glass transition temperature of the sample were tested by differential scanning calorimetry (DSC). The shape memory response temperature, shape memory fixation rate and shape memory recovery rate were tested by dynamic thermal mechanical analyzer (DMA, Q800). The test results are shown in Table 1.

[0048] From the analysis of the results in Table 1, it can be seen that with the increase of the hard segment content, the glass transition temperature of the polyurethane material gradually increases. At the same time, due to the different hard segment contents, there are obvious differences in the glass transition temperatures of the three materials, which provides a basis for achieving different shape memory response temperatures through the glass transition of the materials in subsequent experiments. The self-healing properties and shape memory effects of the three smart materials can meet the diversified and personalized needs of 4D printing.

[0049] Table 1 Self-healing efficiency, melting temperature, glass transition temperature, shape memory response temperature, shape memory fixation rate and shape memory recovery rate of TPU-SMP-1, TPU-SMP-2 and TPU-SMP-3

[0050] TPU-SMP-1 TPU-SMP-2 TPU-SMP-3 Self-repair efficiency (100℃) / % 93.4 89.7 85.4 Melting temperature / ℃ 160 180 207 Glass transition temperature / ℃ 28.9 43.8 64.5 Shape memory response temperature / ℃ 35 50 70 Shape memory fixation rate / % 84.2 92.7 97.4 Shape memory recovery rate / %: 92.5 94.6 95.6

[0051] A multi-response 4D printing method based on self-healing shape memory polyurethane material:

[0052] 1) The self-healing shape memory polyurethane materials prepared above were respectively prepared into filamentous FDM printing wires with a diameter of about 1.75 mm by a micro extruder.

[0053] 2) Figure 1 The overall structure of the humanoid robot model shown is divided into multiple small structures. Figure 1 The left side of the middle arrow shows the overall structure of the humanoid robot model. Figure 1 To the right of the middle arrow is the structural disassembly plan of the humanoid robot model, which has four disconnected parts.

[0054] 3)Reference Figure 2 As shown, the small structure B1 is imported into the FDM printing software, and is printed using the TPU-SMP-1 material using a desktop FDM machine.

[0055] 4)Reference Figure 3 As shown, the small structure B2 is imported into the FDM printing software, and is printed by a desktop FDM machine using the TPU-SMP-2 material.

[0056] 5)Reference Figure 4 As shown, the small structure B3 is imported into the FDM printing software, and is printed by a desktop FDM machine using the TPU-SMP-3 material.

[0057] 6) Using the self-healing property of the polyurethane material, the separately printed small structures B1, B2, and B3 were treated at 100° C. for 20 min to assemble into the overall structure A.

[0058] 7) The assembled overall structure A is heated to 90°C, and then the corresponding small structures B1, B2, and B3 in the overall structure A are pre-programmed into different temporary shapes to obtain the overall structure B; then the overall structure B is placed in ice water at 0°C to fix the pre-programmed temporary shapes.

[0059] 8) The overall structure A (i.e., the overall structure B) with different temporary shapes at different parts is heated from 0°C, and the different shape memory response temperatures of TPU-SMP-1, TPU-SMP-2, and TPU-SMP-3 are used. When the overall structure B is heated to 35°C, the temporary shape of the small structure B1 in the overall structure B is gradually restored. At this time, since the small structures B2 and B3 have not reached the shape memory response temperature, the temporary structures of the small structures B2 and B3 remain unchanged.

[0060] 9) Then, the overall structure B continues to be heated. When the temperature reaches 50°C, the temporary shape of the small structure B2 in the overall structure B gradually recovers. However, since the small structure B3 has not reached the shape memory response temperature, the temporary structure of the small structure B3 remains unchanged.

[0061] 10) Then, the overall structure B continues to be heated. When the temperature reaches 70° C., the temporary shape of the overall structure A corresponding to the small structure B3 is gradually restored, and finally the overall structure B is restored to its original shape, that is, the overall structure A.

[0062] In summary, the present invention synthesizes a polyurethane material with self-repairing properties and shape memory effect through molecular structure design, and splits the overall structure into different small structures, and then uses the polyurethane material with different shape memory response temperatures to print and shape them separately, and at the same time, the multiple small structures that have been printed are assembled into an overall structure using the self-repairing properties of the material and programmed into a temporary shape, and finally, the multiple shape memory effects of the 4D printed object are achieved by controlling the heating temperature of the temporary shape. This new 4D printing method based on different self-repairing shape memory polyurethanes proposed by the present invention will be conducive to promoting the wider application of 4D printing technology in the field of intelligence.

Claims

1. A self-repairing shape memory polyurethane material, characterized in that: The polyurethane material is prepared from diisocyanate, macromolecular diol, benzil dioxime and a catalyst; the molar ratio of the diisocyanate, the macromolecular diol, the benzil dioxime and the catalyst is 100:15-40:60-80:0.1-2.

2. The polyurethane material according to claim 1, characterized in that: The molar ratio of the diisocyanate, the macromolecular diol, the benzildioxime and the catalyst is 100:15-20:70-80:0.5-1.

3. The polyurethane material according to claim 1, 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.

4. The polyurethane material according to claim 1, 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.

5. The polyurethane material according to claim 4, characterized in that: The hydroxyl-terminated polyester diol is one or more of polyadipate small molecule diol ester diol, polycarbonate diol, and polycaprolactone diol; or The hydroxyl-terminated polyether diol is polytetramethylene ether diol and / or polypropylene oxide ether diol.

6. The polyurethane material according to claim 1, characterized in that: The catalyst is one or more of dibutyltin dilaurate, triphenylbismuth and triphenyltin chloride.

7. A method for preparing a self-repairing shape memory polyurethane material as claimed in any one of claims 1 to 6, characterized in that The method comprises: S1: heating the macromolecular diol to remove water to obtain a first intermediate product; S2: cooling the first intermediate product, and adding the diisocyanate thereto to obtain an isocyanate-terminated polyurethane prepolymer; S3: adding the benzildioxime and the catalyst to the isocyanate-terminated polyurethane prepolymer, heating and reacting to obtain a second intermediate product; S4: Casting the second intermediate product into a mold, and vacuum curing to obtain a self-repairing shape memory polyurethane material.

8. The method according to claim 7, characterized in that: In step S1, the reaction temperature is 105-120°C and the reaction time is 1.5-2h; and / or In step S2, the reaction temperature is 60-80°C and the reaction time is 1-2h; and / or In step S3, the reaction temperature is 60-80°C and the reaction time is 1-3h; and / or In step S4, the vacuum curing temperature is 80-100° C., and the vacuum curing time is 8-12 hours.

9. A 4D printing method for the self-repairing shape memory polyurethane material according to any one of claims 1 to 6 or the self-repairing shape memory polyurethane material prepared by the method according to any one of claims 7 to 8, characterized in that: 1) splitting the whole structure to be printed and slicing it using a fused deposition modeling printer to obtain sliced ​​parts; 2) using the self-repairing shape memory polyurethane material with different response temperatures to print the sliced ​​parts respectively, heating them, and assembling them to obtain the overall structure A; 3) heating the overall structure A to obtain an overall structure B assembled from the split parts; 4) cooling the overall structure B; 5) The overall structure B is heated to reach the temperature response threshold of each of the split parts in turn, and the split parts are restored and assembled into the overall structure A in turn.

10. The 4D printing method according to claim 9, characterized in that: In step 3), the temperature is higher than the temperature response threshold of each split part; and / or In step 4), the temperature is lower than the temperature response threshold of each split part.

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