3D-printed self-healing silicone rubber and method for producing same

Abstract

The application belongs to the field of new material science, and provides a 3D-printed self-repairing silicone rubber and a preparation method thereof.The 3D-printed self-repairing silicone rubber mainly comprises hydroxyl-terminated polydimethylsiloxane, diisocyanate, guanidino compound, cross-linking group and solvent.The preparation method of the 3D-printed self-repairing silicone rubber is as follows: hydroxyl-terminated polydimethylsiloxane, catalyst, diisocyanate, guanidino compound and cross-linking agent are sequentially dissolved in the solvent in a certain amount of substance ratio, and then stirred and reacted to obtain a prepolymer;after the reaction is completed, the prepolymer is poured into a mold, and after room temperature curing and heating curing to remove the solvent, the 3D-printed self-repairing silicone rubber material is obtained.The silicone rubber has high mechanical strength and good thermoplasticity, is suitable for various 3D printing processing modes such as fused filament fabrication (FFF), direct ink writing (DIW) and selective laser sintering (SLS), and the printed product is non-toxic and harmless, has a self-repairing function, and is applied to the fields of flexible sensors and biomedical materials.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology and relates to a 3D-printed self-healing silicone rubber and its preparation method. Background Technology

[0002] Polydimethylsiloxane (PDMS) is one of the most promising elastomers due to its excellent thermal stability, biocompatibility, corrosion resistance, flexibility, low cost, ease of use, chemical inertness, biocompatibility, and permeability. Therefore, it can be used in microfluidic systems, biomedical devices, electronic components, filtration and pervaporation membranes, sensors, and coatings.

[0003] Currently, silicone rubber suitable for 3D printing has been reported. CN115637048A discloses a photocurable 3D printing silicone rubber ink and its preparation method. This invention's photocurable 3D printing silicone rubber ink boasts high-precision molding, and its scientifically formulated recipe allows for rapid photocuring, curing within 5 seconds at room temperature, with no noticeable odor or shrinkage after curing. However, the mechanical strength of the photocurable 3D printed silicone rubber products from this invention is low, only 0.6 MPa; the printing method is limited; the residual photoinitiator carries potential biotoxicity; and it lacks dynamic bonds and self-healing properties.

[0004] Based on the above analysis, there is an urgent need in the industry for a self-healing silicone rubber with high mechanical strength, no biological toxicity, and self-healing properties obtained by printing, as well as its preparation method. Summary of the Invention

[0005] In view of the above shortcomings, the purpose of this invention is to address the problems of existing 3D printing methods for silicone rubber being limited in scope, having low mechanical strength, and lacking self-healing properties. This invention provides a self-healing silicone rubber for 3D printing and its preparation method. The guanidinourea dynamic bond, obtained by reacting a guanidinium group with an isocyanate, is a novel thermoresponsive dynamic bond. This allows the cross-linked silicone rubber material to flow upon heating, providing heat-processable properties and enabling its use in fused filament 3D printing. Simultaneously, the dynamic bond reaction enhances the interlayer bonding force of the printed product, reduces the slight anisotropy of the product's mechanical properties, and endows the printed product with self-healing capabilities. The silicone rubber of this invention exhibits excellent mechanical properties, can be used in various 3D printing methods, possesses self-healing functionality, has a simple preparation process, and is relatively low in cost.

[0006] To achieve the above objectives, the present invention employs the following technical means:

[0007] This invention discloses a 3D-printed self-healing silicone rubber, comprising:

[0008] 25-33 parts of hydroxyl-terminated polydimethylsiloxane;

[0009] Catalyst 0.1 to 1 part;

[0010] 33-45 parts of diisocyanate;

[0011] 4 to 23 parts of guanidine compounds;

[0012] 1 to 5 parts of crosslinking agent; and

[0013] Solvent 20-100 parts.

[0014] Furthermore, the hydroxyl-terminated polydimethylsiloxane is one or more of hydroxyl-terminated polydimethylsiloxanes with a molecular weight of 500 to 30,000.

[0015] Furthermore, the catalyst is one or more of triethylamine, dibutyltin dilaurate, N-methylmorpholine, dinonylnaphthalene disulfonic acid, and triphenylphosphine.

[0016] Further, the diisocyanate is one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicycloethylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

[0017] Further, the guanidine compound is one or more of N-[1-amino-1-morpholino-4-ylmethyl-methylene]-guanidine, (1E)-1-[amino-(4-chloro, aniline)methylene]-2-propyl-2-ylguanidine, phenyl biguanide, metformin, tert-butyl ureacarbate, 1-o-toluene biguanide, phenethyl biguanide, and N-phenethyl biguanide.

[0018] Furthermore, the crosslinking agent is one or more of hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, and toluene diisocyanate trimer.

[0019] Furthermore, the solvent is one or more of acetone, isopropanol, ethyl acetate, tetrahydrofuran, 1,4-dioxane, dichloromethane, chloroform, or toluene.

[0020] This invention also discloses a method for preparing 3D-printed self-healing silicone rubber, comprising the following steps:

[0021] (1) Dissolve the raw materials in a solvent in sequence to obtain a reaction solution, and stir the reaction at room temperature for 3 to 9 hours to obtain a prepolymer;

[0022] (2) Pour the prepolymer into a mold, cure it at room temperature for a period of time by removing the solvent, then put it in an oven to remove the solvent and continue curing. After curing, a solid silicone rubber is obtained.

[0023] (3) The solid silicone rubber is sheared and crushed to obtain a 3D printed self-healing silicone rubber.

[0024] Further, the order of adding the raw materials in step (1) is as follows: hydroxyl-terminated polydimethylsiloxane, catalyst, diisocyanate, guanidine compound, and crosslinking agent.

[0025] Furthermore, in step (2), the room temperature curing solvent removal time is 12 to 36 hours, the temperature in the oven is 80°C, and the time for solvent removal and continued curing in the oven is 36 to 72 hours.

[0026] Furthermore, the solvent vapors generated during the solvent removal process of the prepolymer in the oven in step (2) are recovered by a solvent recovery machine.

[0027] The present invention also discloses a 3D-printed self-healing silicone rubber prepared according to any of the above preparation methods.

[0028] The beneficial effects of this invention are as follows:

[0029] 1) In this invention, the guanidine compound in the raw material has polyurea segments on the molecular backbone, which can significantly improve the mechanical strength of the material, and the tensile strength can reach 14.5 MPa.

[0030] 2) In this invention, guanidinium in the 3D-printed self-healing silicone rubber containing guanidinium dynamic bonds is a thermally reversible chemical bond that can break at high temperatures and regenerate when the temperature is lowered. This characteristic gives the prepared cross-linked silicone rubber reprocessable properties.

[0031] 3) In this invention, the 3D-printed self-healing silicone rubber containing guanidinium dynamic bonds has self-healing properties, and the 3D-printed products can achieve damage repair without any external repair agents or catalysts.

[0032] 4) The raw materials used in this invention are readily available, the synthesis process is simple and easy to control, and the yield is high and non-toxic. Attached Figure Description

[0033] Figure 1 The chemical structural formula of the 3D-printed self-healing silicone rubber containing guanidinium dynamic bonds prepared in Example 1;

[0034] Figure 2 The infrared spectrum of the 3D-printed self-healing silicone rubber containing guanidinium urea dynamic bonds prepared in Example 1;

[0035] Figure 3 The image shows the physical specimen of the 3D-printed self-healing silicone rubber containing guanidinium dynamic bonds prepared in Example 1.

[0036] Figure 4 This is a shearing and crushing image of the 3D-printed self-healing silicone rubber containing guanidinium dynamic bonds prepared in Example 1;

[0037] Figure 5 Thermogravimetric curve of the 3D-printed self-healing silicone rubber containing guanidinium urea dynamic bonds prepared in Example 2;

[0038] Figure 6 The strain curves of the 3D-printed self-healing silicone rubber tensile strip containing guanidinium dynamic bonds prepared in Example 2 before and after damage repair are shown.

[0039] Figure 7 This is a temperature-dependent rheological curve of the 3D-printed self-healing silicone rubber containing guanidinium dynamic bonds prepared in Example 2;

[0040] Figure 8 This is a photograph of the 3D-printed self-healing silicone rubber tensile strip containing guanidinium dynamic bonds prepared in Example 3;

[0041] Figure 9 The image shows the stress-strain curve of the 3D-printed self-healing silicone rubber tensile spline containing guanidinium dynamic bonds prepared in Example 3.

[0042] Figure 10 Electron microscope image of the extruded filament of the 3D-printed self-healing silicone rubber filament containing guanidinium dynamic bonds prepared in Example 3. Detailed Implementation

[0043] The 3D printing equipment and raw materials used in the embodiments of this invention are all known products, obtained by purchasing commercially available products. The specific technical solution of this invention is illustrated with reference to the embodiments:

[0044] Example 1

[0045] 1. Preparation of silicone rubber prepolymer

[0046] (1) Weigh out 30 parts of hydroxyl-terminated polydimethylsiloxane (molecular weight 1000), 0.5 parts of dibutyltin dilaurate catalyst, and 39 parts of isophorone diisocyanate in proportion and dissolve them in solvent 1,4-dioxane (25 parts). Stir the reaction at room temperature for 2 hours.

[0047] (2) Weigh 1-o-toluene biguanide (13.5 parts) and solvent 1,4-dioxane (25 parts) according to the proportion and dissolve them in the above reaction solution. Continue stirring at room temperature for 2 hours.

[0048] (3) Finally, weigh out the crosslinking agent hexamethylene diisocyanate trimer (3 parts) and solvent 1,4-dioxane (25 parts) according to the proportion and dissolve them in the above reaction solution. Continue stirring at room temperature for 2 hours.

[0049] (4) Pour the prepolymer obtained in step (3) into a polytetrafluoroethylene mold, cure at room temperature for 24 hours to remove solvent, then place it in an 80°C oven to remove solvent and continue curing for 48 hours. The solvent vapor is recovered by a solvent recovery machine.

[0050] The raw materials and chemical structure of the synthesized silicone rubber in this embodiment are as follows: Figure 1 As shown, the obtained silicone rubber was subjected to infrared spectroscopy detection, and the detection structure is as follows. Figure 2 As shown in Figure 3, the actual object is shown in Figure 4. The particles obtained after shearing and crushing solid silicone rubber are shown in Figure 5. Figure 4 As shown. By Figure 2 It can be seen that the silicone rubber has a chemically cross-linked structure, and the characteristic peak of the isocyanate group in the infrared spectrum is (2240-2280 cm⁻¹). -1 The presence of the '+' sign indicates that all components have reacted completely.

[0051] Example 2

[0052] 1. Preparation of silicone rubber prepolymer

[0053] (1) Weigh out 25 parts of hydroxyl-terminated polydimethylsiloxane (molecular weight 2000), 0.9 parts of triethylamine catalyst and 39 parts of lysine diisocyanate according to the proportion and dissolve them in 20 parts of tetrahydrofuran solvent. Stir the mixture at room temperature for 3 hours.

[0054] (2) Weigh out 15 parts of N-[1-amino-1-morpholin-4-ylmethyl-ylidene]-guanidine and 20 parts of tetrahydrofuran solvent and dissolve them in the above reaction solution. Continue stirring at room temperature for 3 hours.

[0055] (3) Finally, weigh out the crosslinking agent hexamethylene diisocyanate trimer (3 parts) and the solvent tetrahydrofuran (20 parts) according to the proportion and dissolve them in the above reaction solution. Continue stirring at room temperature for 3 hours.

[0056] (4) Pour the prepolymer obtained in step (3) into a polytetrafluoroethylene mold, cure at room temperature for 12 hours to remove solvent, then place it in an 80°C oven to remove solvent and continue curing for 36 hours. The solvent vapor is recovered by a solvent recovery machine.

[0057] The silicone rubber obtained in Example 2 was subjected to thermogravimetric analysis, and the test results are as follows: Figure 5 As shown, the thin neck of the silicone rubber strip molded in Example 2 was cut off with a blade, and then the two ends were glued together and placed in an oven at 110°C for 3 hours. Mechanical testing was then performed, and the results are as follows. Figure 6 As shown. By Figure 5 It can be seen that the initial temperature at which the silicone rubber elastomer experiences weight loss is 211℃, and the weight loss between 211℃ and 303℃ is ~10%, indicating that the silicone rubber synthesized in Example 2 has excellent thermal stability. Figure 6 It is known that the guanidinourea obtained from the reaction of guanidino and isocyanate is a thermoresponsive dynamic bond, which endows silicone rubber products with self-healing properties; damage to the products can achieve 90% self-healing at 110℃. The obtained silicone rubber was subjected to variable-temperature rotational rheology testing, and the test results are as follows... Figure 7 As shown, the viscosity of the silicone rubber drops to zero at around 140°C, indicating that the silicone rubber synthesized in Example 2 has a printing window temperature of approximately 140°C.

[0058] Example 3

[0059] The silicone rubber particles containing guanidinium urea dynamic bonds prepared in Example 1 were used for fused wire fabrication (FFF) 3D printing. The printing parameters were: build chamber (platform) temperature 80°C, screw temperature 135°C, droplet size ratio 1.315, continuous extrusion feed rate 20, continuous extrusion feed rate 65, and internal and external correction factor value 1.0.

[0060] 3D printing stretched splines, such as Figure 8 As shown, the stress-strain curve of the 3D-printed tensile spline is as follows: Figure 9 As shown, an electron microscope image of silicone rubber extruded filaments manufactured by 3D printing filaments is as follows. Figure 10 As shown. The tensile strength of the 3D-printed silicone rubber containing guanidinium urea dynamic bonds in this application can reach 1.5 MPa, which is significantly improved compared with the strength of 0.6 MPa of the existing 3D-printed silicone rubber materials.

[0061] In summary, the guanidinourea dynamic bond of this invention, obtained by the reaction of guanidino groups with isocyanates, is a novel thermoresponsive dynamic bond. This allows the cross-linked silicone rubber material to flow upon heating, providing thermal processability and enabling fused filament 3D printing. Simultaneously, the dynamic bond reaction enhances the interlayer bonding strength of the printed product, reduces the anisotropy of mechanical strength, and endows the printed product with self-healing capabilities; damage to the product can be repaired at 110°C. Furthermore, it improves the mechanical strength of the material. The silicone rubber of this invention exhibits excellent mechanical properties, is suitable for fused filament 3D printing, possesses self-healing capabilities, and has a simple preparation process with relatively low cost. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial applicability.

[0062] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing 3D-printed self-healing silicone rubber, comprising: (1) Dissolve the raw materials in the solvent in sequence to obtain a reaction solution, and stir the reaction at room temperature for 3 to 9 hours to obtain a prepolymer; (2) Pour the prepolymer into a mold, cure at room temperature to remove solvent for a period of time, then put it in an oven to remove solvent and continue curing. After curing, a solid silicone rubber is obtained. (3) The solid silicone rubber is sheared and crushed to obtain a 3D-printed self-healing silicone rubber; wherein: The raw materials are: 25-33 parts of hydroxyl-terminated polydimethylsiloxane, 0.1-1 parts of catalyst, 33-45 parts of diisocyanate, 4-23 parts of guanidine compound, 1-5 parts of crosslinking agent, and 20-100 parts of solvent; The guanidinyl compound is selected from N-[1-amino-1-morpholin-4-ylmethyl-ylidene]-guanidine or 1-o-toluenebiguanidine; The crosslinking agent is one or more of hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, and toluene diisocyanate trimer.

2. The preparation method according to claim 1, wherein: The order of adding the raw materials in step (1) is as follows: hydroxyl-terminated polydimethylsiloxane, catalyst, diisocyanate, guanidine compound, crosslinking agent; The room temperature curing solvent removal time in step (2) is 12~36 hours, the temperature in the oven is 80℃, and the time for solvent removal and continued curing in the oven is 36~72 hours.

3. The preparation method according to claim 1, wherein: The hydroxyl-terminated polydimethylsiloxane is one or more of the hydroxyl-terminated polydimethylsiloxanes with a molecular weight of 500 to 30,000.

4. The preparation method according to claim 1, wherein: The catalyst is one or more of triethylamine, dibutyltin dilaurate, N-methylmorpholine, dinonylnaphthalene disulfonic acid, and triphenylphosphine.

5. The preparation method according to claim 1, wherein: The diisocyanate is one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

6. The self-healing silicone rubber according to claim 1, wherein: The solvent is one or more of acetone, isopropanol, ethyl acetate, tetrahydrofuran, 1,4-dioxane, dichloromethane, chloroform, or toluene.

7. A 3D-printed self-healing silicone rubber prepared by the preparation method according to any one of claims 1 to 6.

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