Preparation method of high-strength high-toughness self-repairing polyurethane

Abstract

The invention discloses a preparation method and application of high-strength and high-toughness self-repairing polyurethane based on dynamic network reconstruction, and belongs to the technical field of self-repairing materials. The method comprises the following steps: synthesizing a prepolymer from polytetrahydrofuran and isophorone diisocyanate, and carrying out composite chain extension through 1, 3-dihydroxyacetone and 4, 7, 10-trioxo-1, 13-tridecane diamine, so as to form a dynamic hydrogen bond network. Excessive hydrogen bond sites are provided through carbonyl of 1, 3-dihydroxyacetone, dynamic network reconstruction can be carried out under external stress stimulation, and the tensile strength, the ductility and the self-repairing efficiency of the material are synchronously improved. After the dynamic network is reconstructed, fracture and recombination of hydrogen bonds can effectively dissipate strain energy and drive damage repair. The tensile strength of the prepared polyurethane reaches 21.1 MPa, the elongation at break exceeds 1500%, the repair efficiency at 60 DEG C for 12 hours is larger than 90%, and the polyurethane is suitable for the field of flexible intelligent electronic equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of self - healing materials, and particularly relates to a preparation method of a high - strength and high - toughness self - healing polyurethane based on dynamic network reconstruction. Background Art

[0002] In the field of future electronic devices, repairable flexible electronic devices are leading the technological trend like bright new stars. With their excellent soft adhesion, bending adaptability, and durability and stability characteristics, they open up new paths for the development of electronic devices. Especially in the future era of artificial intelligence, these devices will profoundly change people's daily lifestyles. To meet diverse application requirements, sensing materials and elastic matrices, as key building elements of stretchable electronic devices, are crucial for realizing this vision. In recent years, polymer elastomers have been widely used in the field of electronic devices due to their unique properties, enhancing mechanical properties and endowing advanced functions such as self - healing.

[0003] Polyurethane is composed of soft segments (such as polyethers, polyesters) and hard segments (urethane or urea groups formed by the reaction of isocyanates and chain extenders). The hard segments provide mechanical strength through hydrogen bonding, crystallization, etc., while the self - healing ability depends on a dynamic reversible hydrogen - bond network. Excess hydrogen - bond acceptor groups (such as ether oxygen groups, carbonyl groups, sulfonyl groups, etc.) can provide more hydrogen - bond binding sites, enhancing the reorganization ability of the dynamic network. When the material is damaged, the broken hydrogen bonds can quickly reform to achieve self - healing.

[0004] However, traditional methods of achieving self - healing by implanting dynamic networks often result in an inability to balance mechanical properties (such as tensile strength and ductility) and self - healing properties. For example: Traditional methods use chain extenders containing urea groups (-NHCONH -) to form a high - density hydrogen - bond network in the hard segments, and scratches can be completely repaired within 24 hours at room temperature. Introducing thiourea groups into the PU hard segments enables rapid self - healing (repair time < 1 hour) through the weak hydrogen - bond action of thiourea, but this strategy sacrifices the mechanical properties of the material because the self - healing ability, ductility, and tensile strength have a competitive dependence on the segmental motion. When improving one property, other properties are often sacrificed. The present invention adopts a dynamic network reconstruction design strategy, implants excess hydrogen - bond acceptor groups in the hard segments, and uses a new 1,3 - dihydroxyacetone (DAC) and 4,7,10 - trioxa - 1,13 - tridecanediamine (TTA) as chain extenders to achieve a synergistic synchronous improvement of mechanical properties and repair efficiency. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a high - strength and high - toughness self - healing polyurethane based on dynamic network reconstruction and its preparation method. The polyurethane prepared by the method of the present invention has excellent mechanical properties and ultra - high self - healing efficiency.

[0006] The design concept of the present invention is as follows: Regarding the problem that the tensile strength, ductility, and self-healing performance of elastomers are mutually contradictory, the fundamental reason is that high tensile strength usually requires strong intermolecular forces and a more compact molecular chain arrangement, which can lead to a decrease in ductility and self-healing performance. This patent adopts a design strategy of dynamic network reconstruction and introduces excess hydrogen bond sites. 1) When facing external stress stimulation, it is beneficial for the re-association of hydrogen bonds during the process of molecular chain slippage to complete dynamic network reconstruction, thereby improving the tensile strength. 2) The disconnection of hydrogen bonds in the new dynamic network can continue to be used to dissipate strain energy, thereby improving ductility. 3) When the material is damaged, the excess hydrogen bond sites can provide sufficient driving force for the repair of the damaged network.

[0007] To achieve the above object, the technical solution adopted in this aspect is as follows: ① Preparation of prepolymer: Dissolve polytetrahydrofuran, isophorone diisocyanate, and the catalyst dibutyltin dilaurate in N,N-dimethylformamide, and react at 60-100 °C for 1-3 hours under nitrogen protection to generate an isocyanate-terminated prepolymer; ② Chain extension reaction: Add a composite chain extender to the prepolymer obtained in step ①. The composite chain extender is a mixture of 1,3-dihydroxyacetone and 4,7,10-trioxa-1,13-tridecanediamine. After adding the composite chain extender, carry out a stirring chain extension reaction at 60-100 °C for 12-36 hours; ③ Molding treatment: Inject the reaction product into a polytetrafluoroethylene mold and perform a drying treatment to obtain a self-healing polyurethane material.

[0008] Among them, the number-average molecular weight of the polytetrahydrofuran is 1000-3000.

[0009] Among them, the molar ratio of the polytetrahydrofuran to the isophorone diisocyanate is 1:2-1:4.

[0010] Among them, in the composite chain extender, the mass fraction ratio of the 1,3-dihydroxyacetone to the 4,7,10-trioxa-1,13-tridecanediamine is 1:1-1:6.

[0011] Among them, the composite chain extender is dissolved in N,N-dimethylformamide and then added to the reaction system.

[0012] Among them, in the composite chain extender, the total amount of the 1,3-dihydroxyacetone and the 4,7,10-trioxa-1,13-tridecanediamine and the molar ratio of the polytetrahydrofuran is 1:1-1:3.

[0013] Among them, in step ③, the drying treatment is carried out by drying at 70-90 °C for 36-72 h.

[0014] Meanwhile, the present invention also provides a composite chain extender for improving the mechanical properties of self-healing polyurethane. The composite chain extender is a mixture of 1,3-dihydroxyacetone and 4,7,10-trioxa-1,13-tridecanediamine. Among them, the molar ratio of the total amount of 1,3-dihydroxyacetone and 4,7,10-trioxa-1,13-tridecanediamine to polytetrahydrofuran is 1:1 to 1:3.

[0015] Beneficial effects

[0016] The present invention relates to a high-performance self-healing polyurethane material based on the reconstruction of a dynamic hydrogen bond network and its preparation method. By using DAC and TTA as composite chain extenders, and using the carbonyl group in the DAC molecule to provide an excessive number of hydrogen bond acceptor sites, a hydrogen bond network system with dynamic characteristics is constructed. Specifically, the ureido / carbamate groups (-NH donor and carbonyl acceptor) formed by the reaction of the chain extender with isocyanate cooperate with the additional carbonyl acceptor provided by DAC to form an optimized hydrogen bond crosslinking network. Under the action of external stress, this combination not only ensures the dynamic dissociation-reconstruction process of hydrogen bonds during the slippage of molecular chains, effectively dissipates strain energy and improves ductility (elongation at break > 1500%), but also ensures the retention of mechanical properties after network reconstruction through the hydrogen bond site redundancy strategy (tensile strength reaches 21.1 MPa). In particular, compared with the traditional multiple hydrogen bond system, the repair efficiency is significantly improved (for example, the repair efficiency of the adipic dihydrazide system at 60°C < 80%). By precisely regulating the hydrogen bond density and distribution, the present invention not only avoids the inhibition of dynamics caused by excessive clustering of hydrogen bonds, but also retains sufficient reversible sites to drive the self-healing process, and finally realizes a self-healing efficiency > 90% at 60°C for 12 hours. During the damage repair process, the redundant hydrogen bond sites act as "repair anchors" for the dynamic network, significantly enhancing the network reconstruction ability of the damaged area. The excellent mechanical-self-healing synergistic properties of this material make it have important application value in the field of flexible intelligent electronic devices. Description of the drawings

[0017] Figure 1 It is the infrared spectrum of Example 1.

[0018] Figure 2 It is the X-ray diffraction pattern of Example 1.

[0019] Figure 3 It is the stress-strain curve of the original spline of Example 1.

[0020] Figure 4 It is the stress-strain curve of the spline of Example 1 after being cut and repaired for different times. Specific implementation manners

[0021] The technical solutions of the present invention are further described below in conjunction with specific embodiments, but the present invention is not limited by the following embodiments.

[0022] The raw materials used in the experiments in the embodiments and comparative examples of the present invention are as follows, but are not limited to the following raw materials. The present invention only uses the following raw materials as specific examples to further illustrate the effect of the high-strength and high-toughness self-healing polyurethane based on dynamic network reconstruction described in the present application:

[0023] Polytetrahydrofuran, PTMG, is available in three types with number average molecular weights of 1000 g / mol, 2000 g / mol, and 3000 g / mol, purchased from MacLean.

[0024] Isophorone diisocyanate, IPDI, was purchased from Maclean.

[0025] N,N-Dimethylformamide and DMF were purchased from Anaiji.

[0026] Dibutyltin dilaurate, DBTDL, was purchased from Aladdin.

[0027] 1,3-Dihydroxyacetone, DAC, was purchased from Maclean.

[0028] 4,7,10-Trioxo-1,13-tridecanediamine, TTA, was purchased from MacLean.

[0029] The performance testing methods in the embodiments and comparative examples of the present invention are as follows.

[0030] Mechanical properties: Tensile strength and elongation at break were tested according to the method specified in GB / T 528-2009 at 25°C and a tensile rate of 100 mm / min. Toughness was calculated from the integral area of ​​the stress-strain curve.

[0031] Mechanical properties and repair rate after repair: Cut the specimen in the middle with a blade, splice the cut surfaces and adjust them at 60℃ for 12h, then test the tensile strength and elongation at break according to the method specified in GB / T 528-2009. Calculate the toughness based on the integral area of ​​the stress-strain curve. Repair rate = elongation of repaired specimen / elongation at break of original specimen × 100%.

[0032] Example 1

[0033] This embodiment provides a method for preparing high-strength and high-toughness self-repairing polyurethane. The number average molecular weight of the polytetrahydrofuran in this embodiment is 2000 g / mol. The specific steps are as follows.

[0034] Step (1): 20 g of PTMG was put into a reactor, and water was removed by vacuum stirring at 90° C. for 1 hour. Nitrogen was introduced for protection, and then 6.8 g of IPDI, 15 mL of DMF and 0.2 g of DBTDL were added. The reaction was continued for 2 hours to obtain an isocyanate-terminated polyurethane prepolymer.

[0035] Step (2): Take 0.5 g of DAC and 3.0 g of TTA, dissolve them in 30 mL of DMF, add them to the prepolymer obtained in Step 1, and continue the reaction at 90 °C for 12 hours. After cooling the reaction system to room temperature, pour it into a polytetrafluoroethylene mold and dry it in a blast dryer at 90 °C for 48 hours to obtain a high-strength and high-toughness self-healing polyurethane.

[0036] After testing, the tensile strength of the original sample bar is 21.1 MPa, the elongation at break is 1592%, and the toughness is 173.7 MJ / m 3 ; the tensile strength of the repaired sample bar is 19.9 MPa, the elongation at break is 1565%, and the toughness is 164.1 MJ / m 3 , and the repair efficiency is 98.3%.

[0037] Example 2

[0038] This example provides a preparation method of a high-strength and high-toughness self-healing polyurethane. The number-average molecular weight of polytetrahydrofuran in this example is 2000 g / mol. The specific steps are as follows.

[0039] Step (1): Take 20 g of PTMG and put it into a reactor. Stir and remove water under vacuum at 90 °C for 1 hour. Introduce nitrogen for protection, then add 6.8 g of IPDI, 15 mL of DMF, and 0.2 g of DBTDL, and continue the reaction for 2 hours to obtain an isocyanate-terminated polyurethane prepolymer.

[0040] Step (2): Take 0.9 g of DAC and 2.2 g of TTA, dissolve them in 30 mL of DMF, add them to the prepolymer obtained in Step 1, and continue the reaction at 90 °C for 12 hours. After cooling the reaction system to room temperature, pour it into a polytetrafluoroethylene mold and dry it in a blast dryer at 90 °C for 48 hours to obtain a high-strength and high-toughness self-healing polyurethane.

[0041] After testing, the tensile strength of the original sample bar is 16.3 MPa, the elongation at break is 1643%, and the toughness is 135.7 MJ / m 3 ; the tensile strength of the repaired sample bar is 15.3 MPa, the elongation at break is 1584%, and the toughness is 122.5 MJ / m 3 , and the repair efficiency is 96.7%.

[0042] Example 3

[0043] This example provides a preparation method of a high-strength and high-toughness self-healing polyurethane. The number-average molecular weight of polytetrahydrofuran in this example is 2000 g / mol. The specific steps are as follows.

[0044] Step (1): Put 20 g of PTMG into the reactor, stir under vacuum to remove water at 90 °C for 1 hour, introduce nitrogen for protection, then add 6.8 g of IPDI, 15 mL of DMF and 0.2 g of DBTDL, and continue to react for 2 hours to obtain an isocyanate-terminated polyurethane prepolymer.

[0045] Step (2): Dissolve 1.3 g of DAC and 1.3 g of TTA in 30 mL of DMF, add it to the prepolymer obtained in Step 1, and continue to react at 90 °C for 12 hours. After cooling the reaction system to room temperature, pour it into a polytetrafluoroethylene mold and dry it in a blast dryer at 90 °C for 48 hours to obtain a high-strength and high-toughness self-healing polyurethane.

[0046] After testing, the tensile strength of the original sample was 11.2 MPa, the elongation at break was 1691%, and the toughness was 102.9 MJ / m 3 ; the tensile strength of the repaired sample was 10.4 MPa, the elongation at break was 1592%, and the toughness was 87.7 MJ / m 3 , and the repair efficiency was 94.1%.

[0047] Comparative Example 1

[0048] This comparative example provides a method for preparing polyurethane. The number-average molecular weight of polytetrahydrofuran in this example is 2000 g / mol, and the specific steps are as follows.

[0049] Step (1): Put 20 g of PTMG into the reactor, stir under vacuum to remove water at 90 °C for 1 hour, introduce nitrogen for protection, then add 6.8 g of IPDI, 15 mL of DMF and 0.2 g of DBTDL, and continue to react for 2 hours to obtain an isocyanate-terminated polyurethane prepolymer.

[0050] Step (2): Dissolve 4.4 g of TTA in 30 mL of DMF, add it to the prepolymer obtained in Step 1, and continue to react at 90 °C for 12 hours. After cooling the reaction system to room temperature, pour it into a polytetrafluoroethylene mold and dry it in a blast dryer at 90 °C for 48 hours to obtain a self-healing polyurethane.

[0051] After testing, the tensile strength of the original sample was 10.9 MPa, the elongation at break was 1597%, and the toughness was 86.1 MJ / m 3 ; the tensile strength of the repaired sample was 10.7 MPa, the elongation at break was 1546%, and the toughness was 80.4 MJ / m 3 , and the repair efficiency was 96.8%.

[0052] Comparative Example 2

[0053] This comparative example provides a method for preparing polyurethane. The number-average molecular weight of polytetrahydrofuran in this example is 2000 g / mol, and the specific steps are as follows.

[0054] Step (1): Put 20 g of PTMG into a reactor, stir and remove water under vacuum at 90 °C for 1 hour, introduce nitrogen for protection, then add 6.8 g of IPDI, 15 mL of DMF, and 0.2 g of DBTDL, and continuously react for 2 hours to obtain an isocyanate-terminated polyurethane prepolymer.

[0055] Step (2): Dissolve 1.8 g of DAC in 30 mL of DMF, add it to the prepolymer obtained in Step 1, and continue to react at 90 °C for 12 hours. After cooling the reaction system to room temperature, pour it into a polytetrafluoroethylene mold and dry it in a blast dryer at 90 °C for 48 hours to obtain self-healing polyurethane.

[0056] After testing, the tensile strength of the original sample is 8.0 MPa, the elongation at break is 960%, and the toughness is 42.1 MJ / m 3 ; the tensile strength of the repaired sample is 7.0 MPa, the elongation at break is 847%, and the toughness is 32.3 MJ / m 3 , and the repair efficiency is 88.3%.

[0057] The performances of Specific Examples 1-3 and Comparative Examples 1-2 are shown in Table 1

[0058]

[0059] Example 4

[0060] This example provides a method for preparing high-strength and high-toughness self-healing polyurethane. The number-average molecular weight of polytetrahydrofuran in this example is 1000 g / mol, and the specific steps are as follows.

[0061] Step (1): Put 20 g of PTMG into a reactor, stir and remove water under vacuum at 60 °C for 2 hours, introduce nitrogen for protection, then add 6.8 g of IPDI, 15 mL of DMF, and 0.2 g of DBTDL, and continuously react for 1 hour to obtain an isocyanate-terminated polyurethane prepolymer.

[0062] Step (2): Dissolve 1.3 g of DAC and 1.3 g of TTA in 30 mL of DMF, add it to the prepolymer obtained in Step 1, and continue to react at 60 °C for 36 hours. After cooling the reaction system to room temperature, pour it into a polytetrafluoroethylene mold and dry it in a blast dryer at 90 °C for 48 hours to obtain high-strength and high-toughness self-healing polyurethane.

[0063] Example 5

[0064] This embodiment provides a method for preparing a high-strength and high-toughness self-healing polyurethane. The number-average molecular weight of the polytetrahydrofuran in this embodiment is 3000 g / mol. The specific steps are as follows.

[0065] Step (1): Put 20 g of PTMG into a reactor, stir under vacuum to remove water at 100 °C for 1.5 hours, introduce nitrogen protection, then add 6.8 g of IPDI, 15 mL of DMF and 0.2 g of DBTDL, and continuously react for 3 hours to obtain an isocyanate-terminated polyurethane prepolymer.

[0066] Step (2): Dissolve 1.3 g of DAC and 1.3 g of TTA in 30 mL of DMF, add them to the prepolymer obtained in Step 1, and continue to react at 100 °C for 12 hours. After cooling the reaction system to room temperature, pour it into a polytetrafluoroethylene mold and dry it in a blast dryer at 70 °C for 36 hours to obtain a high-strength and high-toughness self-healing polyurethane.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing high-strength and high-toughness self-repairing polyurethane, characterized in that: The following steps are involved: ① Preparation of prepolymer: dissolve polytetrahydrofuran, isophorone diisocyanate and catalyst dibutyltin dilaurate in N,N-dimethylformamide, react at 60-100°C for 1-3 hours under nitrogen protection to generate isocyanate-terminated prepolymer; ② Chain extension reaction: adding a composite chain extender to the prepolymer obtained in step ①, wherein the composite chain extender is a mixture of 1,3-dihydroxyacetone and 4,7,10-trioxy-1,13-tridecanediamine, and stirring the mixture at 60-100° C. for chain extension reaction for 12-36 hours; ③ Molding process: inject the reaction product into a polytetrafluoroethylene mold, dry it, and obtain a self-healing polyurethane material.

2. The method for preparing high-strength and high-toughness self-repairing polyurethane according to claim 1, characterized in that: The number average molecular weight of the polytetrahydrofuran is 1000-3000.

3. The method for preparing high-strength and high-toughness self-repairing polyurethane according to claim 1, characterized in that: The molar ratio of the polytetrahydrofuran to isophorone diisocyanate is 1:2 to 1:

4.

4. The method for preparing high-strength and high-toughness self-repairing polyurethane according to claim 1, characterized in that: In the composite chain extender, the mass fraction ratio of the 1,3-dihydroxyacetone to the 4,7,10-trioxy-1,13-tridecanediamine is 1:1 to 1:

6.

5. The method for preparing high-strength and high-toughness self-repairing polyurethane according to claim 1, characterized in that: The composite chain extender is dissolved in N,N-dimethylformamide and then added into the reaction system.

6. The method for preparing high-strength and high-toughness self-repairing polyurethane according to claim 1, characterized in that: In the composite chain extender, the molar ratio of the total amount of 1,3-dihydroxyacetone and 4,7,10-trioxy-1,13-tridecanediamine to polytetrahydrofuran is 1:1-1:

3.

7. The method for preparing high-strength and high-toughness self-repairing polyurethane according to claim 1, characterized in that: In step ③, the drying process is carried out at 70-90° C. for 36-72 hours.

8. A composite chain extender for improving the mechanical properties of self-repairing polyurethane, characterized in that: The composite chain extender is a mixture of 1,3-dihydroxyacetone and 4,7,10-trioxy-1,13-tridecanediamine.

9. The composite chain extender for improving the mechanical properties of self-repairing polyurethane according to claim 8, characterized in that: The molar ratio of the total amount of the 1,3-dihydroxyacetone and the 4,7,10-trioxy-1,13-tridecanediamine to the polytetrahydrofuran is 1:1 to 1:3.

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