Preparation method of high-adhesion self-repairing polyurethane elastomer

Abstract

The invention discloses a preparation method of a high-adhesion self-repairing polyurethane elastomer, which specifically comprises the following steps: taking polytetrahydrofuran glycol and isophorone diisocyanate as raw materials, taking tannic acid and 4, 4 '-diaminodiphenyl disulfide as chain extenders, and adopting a one-pot polymerization method to prepare high-adhesion polyurethane. The polyurethane elastomer is endowed with self-repairing performance by introducing an aromatic group disulfide bond and a dynamic hydrogen bond, the prepared material can complete the repairing process within 2 hours at the temperature of 80 DEG C, and the adhesive force on steel is greater than 10 MPa. A new insight is given to preparation of a high-adhesion self-repairing material, the synthesis method is simple, and the prepared polyurethane has excellent adhesion and self-repairing performance and can be applied to multiple fields.

Description

Technical Field

[0001] The invention belongs to the technical field of new chemical materials, and specifically relates to a method for preparing a high-adhesion self-repairing polyurethane elastomer. Background Art

[0002] Self-healing polymer materials have attracted extensive attention due to their applications in flexible electronics, smart batteries, friction nanogenerators, information encryption and anti-counterfeiting materials, and coatings. Self-healing materials can be divided into two categories according to the different repair methods: external self-healing and intrinsic self-healing. External self-healing materials achieve self-healing by adding functional carriers inside or on the surface of the material. Typical external self-healing materials include liquid-core fiber-type self-healing polymer materials, whose repair mechanism is to encapsulate reactive repair agents in the fibers. When the material is damaged, the repair agent overflows into the matrix material, and the cracks are filled and repaired through the curing and cross-linking reaction between the repair agent and the matrix material. However, external self-healing materials can only be repaired a limited number of times, and the performance of the material may decline after each repair, limiting its potential for long-term application. At the same time, in some external self-healing systems, the repair agent may be at risk of leakage, and once it leaks, it will lose its self-healing ability. Unlike exogenous self-healing materials, intrinsic self-healing materials do not require the addition of functional carriers inside or on the surface of the material, thus avoiding the influence of factors such as the compatibility between the carrier and the substrate, the uniformity of the carrier dispersion, and the content of the repair agent in the carrier. Intrinsic self-healing materials use the molecular structure inside the material that can undergo reversible chemical reactions to achieve self-healing. Intrinsic self-healing polymer materials mainly include reversible covalent bond self-healing and reversible non-covalent bond self-healing. Reversible covalent bond self-healing is achieved by introducing disulfide bonds, imine bonds, Diels-Alder reversible reactions, etc. into the system, while reversible non-covalent bond self-healing is achieved by means of hydrogen bonding, electrostatic effects, ionic effects, and other mechanisms in the system. However, intrinsic self-healing polyurethane elastomers currently have problems such as single function. Functional integration is of great significance for broadening the application range of polymers. For example, high adhesion functionality plays a vital role in many aspects of modern society, such as wearable devices, soft robots, and triboelectric nanogenerators; in particular, the material can achieve high adhesion strength without heating or adding curing agents, which can further improve its applicability and convenience.

[0003] To solve the above problems, by adding tannic acid chain extender to polyurethane elastomer, multiple hydrogen bonds can be generated and strong interfacial interactions with different substrates can be generated to improve adhesion. In addition, the introduced aromatic disulfide bonds can provide better self-healing properties and can complete the repair process within 2 hours at 80°C.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The purpose of the present invention is to overcome the bottleneck of the prior art and provide a method for preparing a high-adhesion self-healing polyurethane elastomer. On the basis of the excellent self-healing ability of the polyurethane elastomer, the elastomer is given high strength and high adhesion properties. The polyurethane elastomer is prepared by a one-pot polymerization method. The polyurethane material is given self-healing properties by introducing multiple hydrogen bonds and disulfide bonds. A large number of hydrogen bonds are introduced and at the same time, because the polyurethane matrix contains a large number of polar groups, it is in close contact with the surface of the substrate to form interfacial hydrogen bonds, thereby increasing adhesion.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical scheme.

[0007] A method for preparing a high-adhesion self-repairing polyurethane elastomer, comprising the preparation of a prepolymer and the preparation of a high-adhesion self-repairing polyurethane elastomer, specifically comprising the following steps: 1) Dewatering polytetrahydrofuran diol (also known as polytetrahydrofuran, PTMEG); 2) After the dehydrated polytetrahydrofuran diol is mixed with an isocyanate monomer, a solvent and a catalyst, the mixture is heated at 70 to 80° C. for 2 to 4 hours in an inert gas (such as nitrogen, argon, etc.) atmosphere to obtain a prepolymer; 3) adding a chain extender and a solvent to the prepolymer obtained in step 2), and then heating at 60 to 90° C. for 2 to 5 hours to obtain a viscous product; 4) The obtained viscous product is vacuum dried to obtain a high-adhesion self-healing polyurethane elastomer.

[0008] Specifically, in step 2), the isocyanate monomer may be isophorone diisocyanate (IPDI) or the like.

[0009] Specifically, in step 2), the catalyst may be dibutyltin dilaurate (DBTDL) or the like.

[0010] Furthermore, in step 3), the chain extender may be one or both of 4,4'-diaminodiphenyl disulfide (APS) and tannic acid (TA).

[0011] Specifically, in step 2) and step 3), the solvent may be N,N -Dimethylformamide (DMF), N,N - dimethylacetamide (DMAC), etc. The mass ratio of the total mass of the raw materials to the mass ratio of the solvent is 1:1 to 3. The raw materials refer to polytetrahydrofuran diol, isocyanate monomer, chain extender and catalyst.

[0012] Specifically, the molar ratio of polytetrahydrofuran diol, isocyanate monomer, chain extender and catalyst can be 50:65-130:10-55:0.2-1.2.

[0013] Furthermore, in step 1), in order to fully remove the water content of the raw material polytetrahydrofuran diol, the polytetrahydrofuran diol can be added to a three-necked flask and then vacuumed for 1 to 2 hours in an oil bath at 110 to 130° C. under the action of an oil pump for dehydration.

[0014] Furthermore, step 4) is performed by heating and drying in a vacuum oven, the drying temperature is 80-110° C., and the drying time is 24-48 hours.

[0015] The present invention also provides a high-adhesion room-temperature self-repairing polyurethane elastomer prepared by the method.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention selects tannic acid and / or 4,4'-diaminodiphenyl disulfide as chain extenders, and the catechol and pyrogallol groups above can form a variety of hydrogen bond interactions with different interfaces, so that they can effectively adhere to different substrates. In addition, the polymer molecular chain bonds can also produce a large number of hydrogen bonds, which accelerate the initial adhesion or interface adhesion during the self-repair process, and the disulfide bond exchange reaction promotes the mutual diffusion of the chains. Aromatic disulfide bonds show better healing properties than aliphatic disulfide bonds.

[0017] The raw materials used in the present invention are all common conventional chemicals with low price, simple synthesis process and convenient operation. The prepared polyurethane elastomer material has high self-healing efficiency and short self-healing time, and also has excellent adhesion ability.

[0018] The present invention uses polytetrahydrofuran diol and isophorone diisocyanate as raw materials, tannic acid and / or 4,4'-diaminodiphenyl disulfide as chain extenders, and dibutyltin dilaurate as a catalyst to synthesize a polyurethane elastomer by condensation polymerization. The polyurethane elastomer material is endowed with self-healing properties by introducing multiple hydrogen bonds and dynamic disulfide bonds, and the repair is completed in a short time (2 h) at 80°C. The present invention provides a new idea for the preparation of self-healing materials and endows them with new functions. The prepared polyurethane has excellent self-healing properties and can exert its application value in various fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The synthetic route of the high-adhesion self-repairing polyurethane elastomer of the present invention is as follows; Figure 2 This is the infrared spectrum of the high-adhesion self-repairing polyurethane elastomer of the present invention; Figure 3 This is the nuclear magnetic hydrogen spectrum of the high-adhesion self-repairing polyurethane elastomer of the present invention; Figure 4 This is the stress-strain curve of the high-adhesion self-repairing polyurethane elastomer of the present invention; Figure 5 This is a picture of the self-repairing process of the high-adhesion self-repairing polyurethane elastomer of the present invention; Figure 6 This is the adhesion diagram of the high adhesion self-healing polyurethane elastomer of the present invention. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described in detail below in conjunction with the embodiments, but the protection scope of the present invention is not limited thereto.

[0021] In the following examples, unless otherwise specified, all raw materials used are common commercially available products that can be directly purchased.

[0022] Embodiment 1: This embodiment provides a method for preparing a room temperature self-healing polyurethane elastomer (synthetic route refers to Figure 1 The specific steps include: First, 4 g (4 mmol) of polytetrahydrofuran diol was added to a three-necked flask and heated under vacuum at 110°C in an oil bath for 2 hours under the action of an oil pump to remove moisture.

[0023] Then, 2.22 g (10 mmol) of isophorone diisocyanate and 20 μL (about 0.0213 g, 0.03 mmol) of dibutyltin dilaurate were dissolved in 5 mL of DMF and injected into the above three-necked flask. Then, under argon conditions, the mixture was heated at 70 ° C for 2.5 hours to obtain a polyurethane prepolymer.

[0024] 0.545 g (2.2 mmol) of 4,4'-diaminodiphenyl disulfide, 1.22 g (0.72 mmol) of tannic acid and 4 mL of DMF were added to the above prepolymer. The reaction system was then maintained at 80°C for another 3 hours to complete the polymerization process and obtain a crude product.

[0025] After the polymerization was completed, the crude product was placed in a vacuum oven at 100 °C and dried for 24 h to obtain the final self-healing polyurethane elastomer, which was recorded as PU-SS-TA.

[0026] Embodiment 2: This embodiment provides a method for preparing a room temperature self-healing polyurethane elastomer (the synthesis route refers to Figure 1 The specific steps are as follows: First, 4 g (4 mmol) of polytetrahydrofuran diol was added to a three-necked flask and heated under vacuum at 110°C in an oil bath for 2 hours under the action of an oil pump to remove moisture.

[0027] Then, 2.22 g (10 mmol) of isophorone diisocyanate and 20 μL (about 0.0213 g, 0.03 mmol) of dibutyltin dilaurate were dissolved in 5 mL of DMF and injected into the above three-necked flask. Then, under argon conditions, the mixture was heated at 70 ° C for 2.5 hours to obtain a polyurethane prepolymer.

[0028] 0.545 g (2.2 mmol) of 4,4'-diaminodiphenyl disulfide and 4 mL of DMF were added to the above prepolymer. The reaction system was then kept at 80°C for another 3 hours to complete the polymerization process and obtain a crude product.

[0029] After the polymerization was completed, the crude product was placed in a vacuum oven at 100 °C and dried for 24 h to obtain the final self-healing polyurethane elastomer, which was recorded as PU-SS.

[0030] Figure 2 The infrared spectra of the two polyurethane elastomers prepared in Examples 1 and 2 are given. It can be seen from the figure that the two elastomers have a peak at 3357 cm -1 The peak at 1591 cm is related to the NH stretching vibration, and its bending vibration appears at 1591 cm -1 1701cm -1 The peak at 1600 cm-1 can be attributed to C=O stretching vibration. The above characteristic peaks confirm the presence of urea and carbamate groups. -1 The peaks near 1200 cm correspond to the frequencies of the aromatic double bonds of tannic acid and 4,4'-diaminodiphenyl disulfide, while the peaks at 1200 cm -1 The absorption peaks around 2270 cm -1 There is no absorption band of -NCO at any place, indicating that all -NCO groups are involved in the reaction.

[0031] Figure 3 The nuclear magnetic resonance hydrogen spectra of two polyurethane elastomers are given. In the PU-SS-TA spectrum, phenol proton peaks corresponding to tannic acid were observed at 8.95-10.23 ppm, and benzene ring proton peaks from TA groups were observed at 6.90-6.93 ppm, which further indicates that tannic acid has been successfully introduced into the target polyurethane skeleton. The absence of these peaks in the PU-SS spectrum indicates that tannic acid is not present in the structure.

[0032] Figure 4The stress-strain curves of the two polyurethane elastomers are given. PU-SS showed poor mechanical properties with a tensile strength of 1.12 MPa and an elongation at break of 1045.86%, while PU-SS-TA had a tensile strength of 21.69 MPa and an elongation at break of 1216.72%. The presence of a rigid aromatic skeleton and multiple hydrogen bonds in the tannic acid structure is expected to provide high tensile strength and toughness.

[0033] Figure 5 The picture of the self-healing process of PU-SS-TA elastomer is given. The specimen was cut into two pieces with a scalpel, and then the two pieces were spliced ​​and placed in an 80℃ environment for 2h. The healing process of the scratched specimen was observed using an optical microscope. After two hours, the cracks on the PU-SS-TA elastomer were almost no longer obvious, indicating that the elastomer has self-healing properties.

[0034] Figure 6 The adhesion diagram of the two polyurethane elastomers is given. It can be seen from the figure that the adhesion of PU-SS-TA on the carbon steel surface is 10.2 Mpa, while the adhesion of PU-SS on carbon steel is only 2.73 Mpa. It can be seen that the addition of tannic acid makes a great contribution to the adhesion of the material.

[0035] In summary, the present invention uses polytetrahydrofuran diol and isophorone diisocyanate as raw materials, tannic acid and 4,4'-diaminodiphenyl disulfide as chain extenders, and adopts a one-pot polymerization method to prepare a high-adhesion polyurethane elastomer. The self-healing property of the polyurethane elastomer is given by introducing aromatic disulfide bonds and dynamic hydrogen bonds. The prepared material can complete the repair process at 80°C within 2 hours, and the adhesion on steel is greater than 10 MPa. The present invention provides new insights into the preparation of high-adhesion self-healing materials, the synthesis method is simple, and the prepared polyurethane elastomer has excellent adhesion and self-healing properties, and can be applied to multiple fields.

Claims

1. A method for preparing a high-adhesion self-repairing polyurethane elastomer, characterized in that: The steps include: 1) subjecting polytetrahydrofuran diol to a dewatering treatment; 2) After the dehydrated polytetrahydrofuran diol is mixed with an isocyanate monomer, a solvent and a catalyst, the mixture is heated at 70 to 80° C. for 2 to 4 hours under an inert gas atmosphere to obtain a prepolymer; 3) adding a chain extender and a solvent to the prepolymer obtained in step 2), and then heating at 60 to 90° C. for 2 to 5 hours to obtain a viscous product; 4) Drying the obtained viscous product to obtain a high-adhesion self-healing polyurethane elastomer.

2. The method for preparing a high-adhesion self-repairing polyurethane elastomer according to claim 1, characterized in that: In step 2), the isocyanate monomer is isophorone diisocyanate.

3. The method for preparing a high-adhesion self-repairing polyurethane elastomer according to claim 1, characterized in that: In step 2), the catalyst is dibutyltin dilaurate.

4. The method for preparing a high-adhesion self-repairing polyurethane elastomer according to claim 1, characterized in that: In step 3), the chain extender is one or both of tannic acid and 4,4'-diaminodiphenyl disulfide.

5. The method for preparing a high-adhesion self-repairing polyurethane elastomer according to claim 1, characterized in that: In step 2) and step 3), the solvent is N,N -dimethylformamide or N,N -Dimethylacetamide.

6. The method for preparing a high-adhesion self-repairing polyurethane elastomer according to claim 1, characterized in that: The molar ratio of polytetrahydrofuran diol, isocyanate monomer, chain extender and catalyst is 50:65-130:10-55:0.2-1.

2.

7. The method for preparing a high-adhesion self-repairing polyurethane elastomer according to claim 1, characterized in that: In step 1), polytetrahydrofuran diol is added into a three-necked flask and then vacuumed in an oil bath at 110-130° C. for 1-2 hours to remove water.

8. The method for preparing a high-adhesion self-repairing polyurethane elastomer according to claim 2, characterized in that: Step 4) Drying in a vacuum oven at a drying temperature of 80 to 110° C. for a drying time of 24 to 48 hours.

9. A high-adhesion self-healing polyurethane elastomer prepared by the method according to any one of claims 1 to 8.

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