Stretchable self-healing thermoplastic polyurethane binder as well as preparation method and application thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a stretchable self-healing thermoplastic polyurethane binder and a preparation method and application thereof.The thermoplastic polyurethane binder is obtained by reacting the following raw materials in parts by mass: 78-94.2 parts of polyether polyol, 4.5-15.4 parts of isocyanate and 1.2-6.6 parts of a chain extender; wherein the chain extender is one of polyhydric alcohols. Wherein the polyether polyol is used as a soft segment to endow the material with excellent flexibility and machinability, the isocyanate is used as a hard segment to form a cross-linked structure or a crystal domain to significantly improve the mechanical strength of the material, and microphase separation occurs between the isocyanate and the soft segment to further optimize the performance balance, and in addition, the chain extender is used for prolonging the molecular chain or increasing the cross-linking density to further improve the mechanical strength of the material. The physical properties of the material are effectively regulated and controlled; by introducing the chain extender containing polar groups, dynamic covalent bonds or multiple hydrogen bonds can be formed in an interface region between soft and hard segments, so that the hydrogen bond density is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a stretchable self-healing thermoplastic polyurethane adhesive and a preparation method and application thereof. Background Art

[0002] In supercapacitor energy storage electronic devices, the choice of binder is crucial; thermoplastic polyurethane (TPU) binders have been widely used in many fields such as construction, electronics and automobiles due to their excellent elasticity, wear resistance and chemical resistance. Existing technologies mainly focus on improving the bonding strength, durability and environmental stability of TPU binders by adding nanofillers (such as carbon nanotubes and graphene) and introducing dynamic chemical bonds (such as hydrogen bonds and dynamic covalent bonds).

[0003] In addition, current research is also dedicated to improving the self-healing ability and conductivity of polyurethane adhesives to meet the needs of emerging fields such as flexible electronic devices and wearable devices. However, the existing adhesives on the market have the limitation of slow self-healing speed, which makes it difficult to complete the repair in a short time. Furthermore, the synthesis process of existing polyurethane materials is relatively complicated and the production cost is high, which to a certain extent limits its large-scale application. In addition, the existing adhesives also have the problems of insufficient bonding strength and poor acid and alkali resistance.

[0004] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a stretchable self-healing thermoplastic polyurethane adhesive and a preparation method and application thereof, aiming to solve the problems of insufficient bonding strength, poor acid and alkali resistance and poor self-healing performance of existing adhesives.

[0006] The technical solution of the present invention is as follows:

[0007] A stretchable self-healing thermoplastic polyurethane adhesive is obtained by reacting the following raw materials in parts by weight: 78-94.2 parts of polyether polyol, 4.5-15.4 parts of isocyanate, and 1.2-6.6 parts of chain extender;

[0008] Wherein, the chain extender is one of the polyols.

[0009] The stretchable self-healing thermoplastic polyurethane adhesive, wherein the molar mass of the polyether polyol is between 2000 g / mol and 8000 g / mol; the polyether polyol comprises at least one of the following structural formulas:

[0010]

[0011] The stretchable self-healing thermoplastic polyurethane adhesive, wherein the isocyanate is an aromatic isocyanate; the aromatic isocyanate includes at least one of the following structural formulas:

[0012]

[0013] The stretchable self-healing thermoplastic polyurethane adhesive, wherein the chain extender comprises at least one of the following structural formulas:

[0014]

[0015] The stretchable self-healing thermoplastic polyurethane adhesive is obtained by reacting the following raw materials in parts by mass: 79 parts of polyether polyol, 15 parts of isocyanate, and 6 parts of chain extender.

[0016] A method for preparing a stretchable self-healing thermoplastic polyurethane adhesive comprises the following steps:

[0017] The polyether polyol and isocyanate are mixed and subjected to polymerization reaction to obtain a polymer precursor;

[0018] The polymer precursor and the chain extender are heated and stirred to obtain a transparent colloid polyurethane material through a chain extension reaction;

[0019] The transparent colloid polyurethane material is mixed with an organic solvent to obtain a thermoplastic polyurethane adhesive.

[0020] The method for preparing the stretchable self-healing thermoplastic polyurethane adhesive, wherein the polymerization reaction temperature is 80° C.-100° C., and the polymerization reaction time is 2 h-22 h.

[0021] The preparation method of the stretchable self-healing thermoplastic polyurethane adhesive, wherein the heating and stirring temperature is 80°C-100°C, and the heating and stirring time is 20min-30min; the chain extension reaction temperature is 120°C-130°C, and the chain extension reaction time is 8h-11h.

[0022] Application of a stretchable self-healing thermoplastic polyurethane adhesive in supercapacitors or electrochemical energy storage devices.

[0023] The application described above, wherein the electrode material in the electrochemical energy storage device includes a positive electrode active material or a negative electrode active material, and the thermoplastic polyurethane binder and a conductive agent; the mass ratio of the positive electrode active material or the negative electrode active material to the thermoplastic polyurethane binder and the conductive agent is (66.7-97.2):(2.8-25):(0-9.4).

[0024] Beneficial effects: The present invention provides a stretchable self-healing thermoplastic polyurethane binder and its preparation method and application. The stretchable self-healing thermoplastic polyurethane binder is obtained by reacting the following raw materials of mass number: polyether polyol 78-94.2, isocyanate 4.5-15.4, chain extender 1.2-6.6; wherein the chain extender is one of the polyols. The thermoplastic polyurethane binder of the present invention can be used to replace the existing polytetrafluoroethylene (PTFE) binder, wherein the polyether polyol is used as a soft segment to give the material excellent flexibility and processability, and the isocyanate is used as a hard segment to form a cross-linked structure or a crystal domain, which significantly improves the mechanical strength of the material, and at the same time, microphase separation occurs between the soft segment, further optimizing the performance balance, and the chain extender effectively regulates the physical properties of the material by extending the molecular chain or increasing the cross-linking density, including hardness, adhesion and wear resistance. In addition, by introducing a chain extender containing a polar group, dynamic covalent bonds or multiple hydrogen bonds can be formed between the soft and hard segments in the interface area, thereby significantly improving the hydrogen bond density. This design can effectively enhance the self-healing properties of the material and further improve the mechanical strength and adhesion while ensuring flexibility. In addition, the binder can meet the electrochemical performance requirements of stretchable devices, and its preparation process is simple, environmentally friendly and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a schematic diagram of a process flow of a method for preparing a stretchable self-healing thermoplastic polyurethane adhesive;

[0026] Figure 2 The synthetic route for synthesizing the stretchable self-healing thermoplastic polyurethane adhesive in Example 1;

[0027] Figure 3 This is a comparison diagram of the mechanical properties of the thermoplastic polyurethane adhesive prepared in Example 1 before and after self-healing;

[0028] Figure 4 The schematic diagram of the simulated structure of preparing a fabric-based stretchable supercapacitor using the thermoplastic polyurethane binder prepared in Example 1;

[0029] Figure 5 This is a physical picture of a fabric-based stretchable supercapacitor prepared using the thermoplastic polyurethane binder prepared in Example 1;

[0030] Figure 6 This is a test diagram of the anti-fatigue mechanical properties of the thermoplastic polyurethane adhesive prepared in Example 1;

[0031] Figure 7 This is a test diagram of the self-healing performance of the thermoplastic polyurethane adhesive prepared in Example 1;

[0032] Figure 8This is a comparison chart of the capacity retention rate of the polyurethane binder material prepared in Example 1 and the button supercapacitor prepared in Comparative Example 1;

[0033] Fig. 9 This is a comparison chart of the rate performance of the polyurethane binder material prepared in Example 1 and the button supercapacitor prepared in Comparative Example 1;

[0034] Fig.10 This is a comparison chart of the elongation at break of the thermoplastic polyurethane adhesive prepared in Example 5 and Example 1;

[0035] Fig.11 The fluorine nuclear magnetic resonance spectrum test diagram of the thermoplastic polyurethane prepared in Example 5 and Example 1;

[0036] Fig.12 This is a thermogravimetric analysis test chart of the thermoplastic polyurethane prepared in Example 5 and Example 1. DETAILED DESCRIPTION

[0037] The present invention provides a stretchable self-healing thermoplastic polyurethane adhesive and a preparation method and application thereof. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0038] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as herein.

[0039] Electrochemical energy storage devices, such as supercapacitors, are gradually replacing traditional chemical power sources and becoming one of the most important energy storage technologies of this century due to their advantages of fast charging and discharging speed, long cycle life, wide applicable temperature range and environmental protection. At present, supercapacitors have been widely used in high-tech fields such as portable electronic products, electronic transportation vehicles and wearable energy storage devices, bringing unprecedented development opportunities to the supercapacitor material industry.

[0040] In supercapacitor energy storage electronic devices, the selection of binder is crucial. However, existing binders still have the following problems that need to be solved:

[0041] 1) Insufficient bonding strength: As the number of cycles of energy storage devices such as supercapacitors increases, the bonding strength will gradually decrease, resulting in device capacity decay. When the electrode is subjected to external force, insufficient bonding strength may cause the electrode material to fall off and destroy the conductive path.

[0042] 2) Poor acid and alkali resistance: Existing materials have limited performance in acid and alkali resistance and can only work in mild environments, which affects their wide application.

[0043] 3) Poor self-healing performance: After the electrode is damaged, it is difficult for the binder to quickly restore its mechanical properties, affecting the long-term stability of the energy storage device.

[0044] 4) Complex preparation process and high cost: The synthesis process of polyurethane adhesive is relatively complicated, resulting in high cost in large-scale production, limiting its widespread application in industry.

[0045] Therefore, future research should focus on improving the self-healing properties of polyurethane binders, optimizing their electrochemical performance in a stretched state, and reducing their production costs to promote their widespread application in supercapacitors and other electronic devices.

[0046] Based on this, the present invention provides a stretchable self-healing thermoplastic polyurethane adhesive, which is obtained by reacting the following raw materials in parts by weight: 78-94.2 parts of polyether polyol, 4.5-15.4 parts of isocyanate, and 1.2-6.6 parts of chain extender; wherein the chain extender is one of the polyols.

[0047] In the present embodiment, the thermoplastic polyurethane binder can be used to replace the existing polytetrafluoroethylene (PTFE) binder, wherein polyether polyol is used as a soft segment, giving the material excellent flexibility and processability, and isocyanate is used as a hard segment to form a cross-linked structure or a crystalline domain, significantly improving the mechanical strength of the material, while microphase separation occurs between the soft segment, further optimizing the performance balance, and the chain extender effectively regulates the physical properties of the material by extending the molecular chain or increasing the cross-linking density, including hardness, adhesion and wear resistance. In addition, by introducing a chain extender containing a polar group (such as a fluorinated group or a plurality of hydroxyls), a dynamic covalent bond or multiple hydrogen bonds (such as hydrogen-fluorine bonds) can be formed between the soft and hard segments in the interface region, thereby significantly improving the hydrogen bond density. This design can effectively enhance the self-healing properties of the material, and further improve the mechanical strength and adhesion while ensuring flexibility. In addition, the binder can meet the requirements of the stretchable device for electrochemical performance, and its preparation process is simple, environmentally friendly and low cost. When the thermoplastic polyurethane binder is applied to stretchable supercapacitors, it exhibits excellent cycle stability and high coulombic efficiency; at the same time, the binder can also be extended to a variety of electrochemical energy storage devices, such as lithium-ion batteries, lithium-sulfur batteries, aqueous zinc-ion batteries, etc.

[0048] Specifically, compared with the existing PTFE binder, the thermoplastic polyurethane binder provided by the present invention has better self-healing performance, can quickly restore to its original state after the external force is removed, and has stronger adhesion. It can ensure that the electrochemical properties of the electrode remain stable in the stretched state, reduce the shedding of the electrode material and the loss of the conductive path, and make the stretchable supercapacitor show better cycle stability and coulomb efficiency; and the production process of the thermoplastic polyurethane binder is simple, environmentally friendly, low-cost, and has good application value.

[0049] In some embodiments, the thermoplastic polyurethane binder is prepared by stepwise polymerization of polyether polyol, isocyanate and chain extender, and its molecular formula can be expressed as represents polyether polyol, isocyanate and chain extender respectively.

[0050] In some embodiments, the molar mass of the polyether polyol is between 2000 g / mol and 8000 g / mol; the polyether polyol includes but is not limited to at least one of the following structural formulas:

[0051]

[0052] Specifically, polyether polyols have a highly flexible molecular chain structure, which can significantly enhance the microphase separation between soft and hard segments, thereby improving the self-healing properties of the material; at the same time, their low glass transition temperature (Tg) helps optimize the processing technology and ensure the efficient preparation of the material. In addition, polyether polyols do not contain ester groups, show stronger water permeability, and give thermoplastic polyurethane excellent hydrolysis resistance. Its good durability effectively improves the material's fatigue resistance, and its lower hysteresis loss gives it higher energy resilience under dynamic loading. In addition, polyether polyols also have strong chemical stability, which can extend the service life of the material and show excellent comprehensive performance in extreme environments.

[0053] In some embodiments, the isocyanate is an aromatic isocyanate; the aromatic isocyanate includes but is not limited to at least one of the following structural formulas:

[0054]

[0055] Specifically, aromatic isocyanates, due to their rigid conjugated aromatic ring structure, can form stable hard segments, enhance molecular packing density, improve the tensile strength, hardness and modulus of the material, and provide stable mechanical support through clear soft and hard segment microphase separation; their structural stability gives the material a higher glass transition temperature and thermal decomposition temperature, allowing the binder to maintain performance at high temperatures. At the same time, the polar -NCO group and the surface active groups of the substrate (such as -OH, -NH 2, -COOH) to form covalent bonds or hydrogen bonds to enhance adhesion; in addition, the chemical inertness and UV resistance of the aromatic ring improve the material's anti-aging properties and extend its service life. The high stacking density of the hard segment reduces hysteresis loss, improves dynamic resilience and fatigue resistance, and enhances the material's acid, alkali and solvent resistance, making it suitable for complex application scenarios.

[0056] In some embodiments, the chain extender includes but is not limited to at least one of the following structural formulas:

[0057]

[0058] Specifically, the chain extender enhances the crosslinking density and the interaction force between molecular chains in the material by introducing hydrogen bonds or dynamic covalent bonds with strong polarity (such as hydrogen-fluorine bonds), thereby significantly improving the mechanical strength and self-healing efficiency of thermoplastic polyurethane; the rigidity of the aromatic ring helps to further enhance the mechanical properties of polyurethane, and at the same time, the -NCO group in the aromatic isocyanate can react with the surface active groups of the substrate (such as -OH, -NH 2 , -COOH) to form covalent bonds or hydrogen bonds, thus improving the material's adhesion, glass resistance, hardness, tensile strength, compressive strength and modulus. Chain extenders with multiple hydroxy groups provide multiple reaction sites to promote the reaction of isocyanate with multiple hydroxy groups, forming more cross-linking points and increasing the cross-linking density, thereby improving the material's molecular weight and structural stability, and enhancing its wear resistance, aging resistance and durability.

[0059] In a preferred embodiment, the chain extender is a fluorine-containing chain extender.

[0060] In some embodiments, the adhesive is obtained by reacting the following raw materials in mass fractions: 79 parts of polyether polyol, 15 parts of isocyanate, and 6 parts of chain extender. The adhesive prepared in this mass fraction can better achieve self-healing properties by introducing sufficient reversible covalent bonds in the polyurethane molecular segments.

[0061] In addition, Figure 1 As shown, the present invention also provides a method for preparing a stretchable self-healing thermoplastic polyurethane adhesive, comprising the steps of:

[0062] Step S10: mixing polyether polyol and isocyanate, and obtaining a polymer precursor after polymerization reaction;

[0063] Step S20: heating and stirring the polymer precursor and the chain extender to obtain a transparent colloid polyurethane material through a chain extension reaction;

[0064] Step S30: mixing the transparent colloid polyurethane material with an organic solvent to obtain a thermoplastic polyurethane adhesive.

[0065] In this embodiment, the preparation method has the characteristics of simple process, low cost and simple structural design. It overcomes the problems of poor self-healing performance, complex synthesis process, insufficient bonding performance and low electrochemical stability under stretching of existing thermoplastic polyurethane adhesives, and demonstrates unique advantages and broad application prospects in the field of stretchable devices.

[0066] Compared with the prior art, the thermoplastic polyurethane adhesive provided by the present invention has the following functions and advantages:

[0067] 1) Achieved excellent self-healing performance, significantly improving the life and reliability of the material during use;

[0068] 2) Provides strong adhesion, enhances adhesion to electrode materials, and further improves energy storage performance, especially maintaining electrochemical stability under stress conditions;

[0069] 3) Simplified soft and hard segment structure design and preparation process are adopted, which is easy for industrial application;

[0070] 4) By selecting different chain extenders, thermoplastic polyurethane materials with different mechanical strengths and electrochemical properties can be prepared, thereby meeting the needs of different application scenarios.

[0071] In some embodiments, the polymerization reaction temperature is 80° C.-100° C., and the polymerization reaction time is 2 h-22 h. Under this condition, the polyether polyol and the isocyanate can undergo a polymerization reaction to form a polymer precursor through bonding.

[0072] In a preferred embodiment, the polymerization reaction temperature is 80° C., and the polymerization reaction time is 2 h.

[0073] In some embodiments, the heating and stirring temperature is 80°C-100°C, and the heating and stirring time is 20min-30min; the chain extension reaction temperature is 120°C-130°C, and the chain extension reaction time is 8h-11h. Heating and stirring can improve the mixing uniformity of the polymer precursor and the chain extender, and then the chain extension reaction is performed to cause a polymerization reaction between the polymer precursor and the chain extender to obtain a stretchable self-healing thermoplastic polyurethane adhesive.

[0074] In some embodiments, the organic solvent is one of DMF and DMSO, which can effectively dissolve the thermoplastic polyurethane binder to obtain a liquid binder.

[0075] In some embodiments, the solid content of the thermoplastic polyurethane binder is 20wt%; low concentration (5wt%) is suitable for rapid curing and film formation; medium concentration (30wt%) is suitable for conventional coating or binder applications, balancing coating thickness, adhesion and mechanical properties; high concentration (30wt%-50wt%) is suitable for industrial coatings with enhanced mechanical properties or thick coatings. In this embodiment, a 20wt% polyurethane binder with moderate viscosity is used to ensure uniform coating, regulate electrode coating thickness, and help improve conductivity, ion migration efficiency and battery performance. It can balance adhesion and mechanical properties, avoid electrode breakage due to expansion and contraction, enhance cycle stability and capacity retention, and moderate curing time ensures that the electrode material is uniformly coated and smoothly cured after coating, which is convenient for subsequent drying processes.

[0076] In addition, the present invention also provides an application of a stretchable self-healing thermoplastic polyurethane adhesive in a supercapacitor or an electrochemical energy storage device.

[0077] In this embodiment, the thermoplastic polyurethane binder has better self-healing properties, can quickly restore to its original state after the external force is removed, and has stronger adhesion. It can ensure that the electrochemical properties of the electrode remain stable in the stretched state, reduce the shedding of electrode materials and the loss of conductive paths, and enable stretchable supercapacitors and electrochemical energy storage devices to exhibit better cycle stability and coulombic efficiency.

[0078] In some embodiments, the electrochemical energy storage device includes a lithium-ion battery, a lithium-sulfur battery, an aqueous zinc-ion battery, and the like.

[0079] In some embodiments, the electrode material in the electrochemical energy storage device includes a positive electrode active material or a negative electrode active material, and the thermoplastic polyurethane binder and the conductive agent; the mass ratio of the positive electrode active material or the negative electrode active material to the thermoplastic polyurethane binder and the conductive agent is (66.7-97.2):(2.8-25):(0-9.4).

[0080] Specifically, the positive electrode active material or the negative electrode active material is mixed with a binder and a conductive agent, and after being uniformly mixed in a homogenizer, it is coated on a fabric current collector using a scraper to obtain an electrode positive electrode material or an electrode negative electrode material.

[0081] In some embodiments, the positive electrode active material is but not limited to one of activated carbon or hard carbon; the negative electrode active material is but not limited to MXene.

[0082] In some embodiments, the conductive agent is, but is not limited to, a conductive carbon black material; and the current collector is, but is not limited to, a stretchable current collector of a fabric substrate.

[0083] The following examples are further given to illustrate the present invention in detail. It should also be understood that the following examples 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 by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention.

[0084] Example 1

[0085] In this embodiment, polypropylene glycol (Mw=2000) is used as the soft segment, 2,4-toluene diisocyanate is used as the hard segment, and 2,2,3,3,4,4-hexafluoro-1,5-pentanediol is used as the chain extender to prepare a stretchable self-healing thermoplastic polyurethane adhesive, whose molecular structure is: Its synthetic route is Figure 2 As shown, the specific steps are as follows:

[0086] 1) Pour 10 g of polypropylene glycol into a pressure bottle, place it in an oil bath at 100°C, and evacuate the bottle under nitrogen atmosphere for 30 minutes;

[0087] 2) Then, the temperature of the oil bath was lowered to 80°C, and 1.91 g of 2,4-toluene diisocyanate (2,4-TDI) was added to the pressure bottle, and the reaction was carried out for 2 hours;

[0088] 3) Keeping the reaction temperature constant, add 4.24 g of acetonitrile solution of 2,2,3,3,4,4-hexafluoro-1,5-pentanediol (acetonitrile accounts for 80 wt%) into the pressure bottle and stir for 0.5 hour;

[0089] 4) After stirring evenly, the solution was poured into a square silicone mold, vacuum desolventized and chain extended at 130° C. for 10 hours to obtain a transparent, colloid-like thermoplastic polyurethane material A1.

[0090] Figure 3 Corresponding to the thermoplastic polyurethane material A1 prepared in this embodiment, it can be seen that after the dumbbell-shaped material is sheared and self-healed by heating, it is stretched again by applying external force, and the material still has good elasticity.

[0091] Figure 4 and Figure 5 The schematic diagram and the actual picture of the fabric-based stretchable supercapacitor prepared by using the thermoplastic polyurethane binder prepared in Example 1 are shown. As can be seen in the figure, the thermoplastic polyurethane binder prepared in this example is combined with activated carbon and MXene materials to prepare the positive and negative electrodes of the supercapacitor. 2 SO 4 The fabric-based supercapacitor can be stretched to a certain length while maintaining stable electrochemical performance, proving that it still has excellent electrochemical performance and stability in the stretched state.

[0092] The anti-fatigue mechanical performance test graph and self-healing performance test graph of the thermoplastic polyurethane adhesive prepared in Example 1 are shown in FIG. Figure 6 and Figure 7 As shown, it is shown that the thermoplastic polyurethane adhesive prepared in this embodiment has good anti-fatigue mechanical properties and self-healing ability.

[0093] Comparative Example 1

[0094] A commercially available conventional binder PTFE is used.

[0095] Example 2

[0096] The thermoplastic polyurethane binder prepared in Example 1 was dissolved in dimethylformamide and used as a binder material to prepare a button supercapacitor with activated carbon as a positive electrode material. After 16,000 cycles of charge and discharge, its stability and capacity retention rate were higher than those of the same type of PTFE binder.

[0097] Figure 8 The capacity retention rates of the button supercapacitors prepared by the polyurethane binder material of Example 1 and the comparative example 1 (PTFE material) are shown. It can be seen from the figure that the supercapacitor prepared in this example shows significantly higher stability in capacity retention rate. Fig. 9 The rate performance of supercapacitors prepared using two binders at different current densities was demonstrated, and the results showed that the supercapacitor prepared in this example could recover to its initial capacity level under different current density tests, while the capacity of the PTFE material decreased. These results show that the thermoplastic polyurethane binder of Example 1 has better energy storage and electrochemical properties.

[0098] Example 3

[0099] In this embodiment, polypropylene glycol (Mw=8000) is used as a soft segment, 2,4-toluene diisocyanate is used as a hard segment, and 2,2,3,3,4,4-hexafluoro-1,5-pentanediol is used as a chain extender to prepare a stretchable self-healing thermoplastic polyurethane adhesive, which specifically includes the following steps:

[0100] 1) Pour 15 g of polypropylene glycol into a pressure bottle, place it in a 100°C oil bath, and stir under a nitrogen atmosphere for 30 minutes;

[0101] 2) then adding 0.718 g of 2,4-toluene diisocyanate to react for 22 hours;

[0102] 3) Cool the reaction system to 80° C., add 1.59 g of acetonitrile solution of 2,2,3,3,4,4-hexafluoro-1,5-pentanediol (80 wt % acetonitrile) into the pressure bottle, and stir for 0.5 hour;

[0103] 4) After stirring evenly, vacuum desolventizing was performed and chain extension reaction was carried out at 130° C. for 10 hours to obtain a yellow transparent thermoplastic polyurethane adhesive A2.

[0104] Example 4

[0105] In this embodiment, polytetrahydrofuran (Mw=2000) is used as a soft segment, 2,4-toluene diisocyanate is used as a hard segment, and diethylene glycol is used as a chain extender to prepare a stretchable self-healing thermoplastic polyurethane adhesive, which specifically includes the following steps:

[0106] 1) Pour 12 g of polypropylene glycol into a pressure bottle, place it in a 100°C oil bath, and stir under a nitrogen atmosphere for 30 minutes;

[0107] 2) The temperature of the oil bath was then lowered to 80° C., and 2.3 g of 2,4-toluene diisocyanate was added to react for 2 hours;

[0108] 3) Add 3.18 g of diethylene glycol in acetonitrile solution (80 wt % acetonitrile) into the pressure bottle and stir for 0.5 hour;

[0109] 4) After the mixture is stirred and polymerized uniformly, vacuum desolventization is performed and a chain extension reaction is carried out at 120° C. for 10 hours to obtain a white and transparent thermoplastic polyurethane adhesive A3.

[0110] Example 5

[0111] In this embodiment, polypropylene glycol (Mw=2000) is used as a soft segment, 2,4-toluene diisocyanate is used as a hard segment, and diethylene glycol is used as a chain extender to prepare a stretchable self-healing thermoplastic polyurethane adhesive, which specifically includes the following steps:

[0112] 1) Pour 15 g of polypropylene glycol into a pressure bottle, place it in a 100°C oil bath, and stir under a nitrogen atmosphere for 30 minutes;

[0113] 2) The temperature of the oil bath was then lowered to 80° C., and 2.87 g of 2,4-toluene diisocyanate was added to react for 2 hours;

[0114] 3) Add 0.79 g of acetonitrile solution of diethylene glycol (80 wt % acetonitrile) into the pressure bottle and stir for 0.5 hour;

[0115] 4) After the mixture is stirred and polymerized uniformly, vacuum desolventization is performed and a chain extension reaction is carried out at 120° C. for 10 hours to obtain a white and transparent thermoplastic polyurethane adhesive A4.

[0116] The mechanical and electrochemical properties of the thermoplastic polyurethane adhesive prepared in this embodiment were tested, and the tensile strength was up to 5.7 MPa, and the maximum elongation at break was about 2500%. In addition, the thermoplastic polyurethane adhesive has good healing properties, and the mechanical healing ability is consistent with that of self-healing polyurethane, and can be healed by heating for 5 seconds after cutting.

[0117] Fig.10 The elongation at break test results of the thermoplastic polyurethane adhesive prepared in Example 5 and Example 1 are shown. The results show that both Example 1 and Example 5 can be stretched to 2500% in length and can be fully recovered to the initial length, showing excellent resilience. When stretched to 1000%, the mechanical strength of Example 1 exceeds that of Example 5, and finally reaches 0.63MPa, which is significantly higher than that of Example 5. This result shows that the thermoplastic polyurethane adhesive of Example 1 forms stronger chemical bonds (such as hydrogen-fluorine bonds and multiple hydrogen bonds) in the molecules, thereby significantly improving the mechanical strength of the material.

[0118] The fluorine nuclear magnetic resonance spectrum test graph and the thermogravimetric analysis test graph of the thermoplastic polyurethane prepared in Example 5 and Example 1 are as follows: Fig.11 and Fig.12 As shown, the spectrum of the polymer shows two absorption peaks, located at -121.3ppm and -125.6ppm, indicating the presence of fluorine atoms. In contrast, no fluorine absorption peaks were observed in the spectrum of the control sample PU-2kDEG. The decomposition temperature of A1 is 271℃, which is higher than 258℃ of A4. This indicates that A1 has stronger intermolecular interactions inside its matrix, thereby improving its thermal stability.

[0119] In summary, the present invention provides a kind of stretchable self-healing thermoplastic polyurethane adhesive and its preparation method and application, and the stretchable self-healing thermoplastic polyurethane adhesive is obtained by reacting the following raw materials by mass: 78-94.2 parts of polyether polyol, 4.5-15.4 parts of isocyanate, and 1.2-6.6 parts of chain extender; wherein, the chain extender is one of the polyols. The thermoplastic polyurethane adhesive of the present invention can be used to replace the existing polytetrafluoroethylene (PTFE) adhesive, wherein the polyether polyol is used as a soft segment, giving the material excellent flexibility and processability, and the isocyanate is used as a hard segment to form a cross-linked structure or a crystalline domain, significantly improving the mechanical strength of the material, and at the same time, microphase separation occurs between the soft segment, further optimizing the performance balance, and the chain extender effectively regulates the physical properties of the material by extending the molecular chain or increasing the cross-linking density, including hardness, adhesion and wear resistance. In addition, by introducing a chain extender containing a polar group, dynamic covalent bonds or multiple hydrogen bonds can be formed between the soft and hard segments in the interface region, thereby significantly improving the hydrogen bond density. This design can effectively enhance the self-healing properties of the material and further improve the mechanical strength and adhesion while ensuring flexibility. In addition, the binder can meet the electrochemical performance requirements of stretchable devices, and its preparation process is simple, environmentally friendly and low-cost.

[0120] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A stretchable self-healing thermoplastic polyurethane adhesive, characterized in that: Obtained by reacting the following raw materials in parts by weight: 78-94.2 parts of polyether polyol, 4.5-15.4 parts of isocyanate, and 1.2-6.6 parts of chain extender; Wherein, the chain extender is one of the polyols.

2. The stretchable self-healing thermoplastic polyurethane adhesive according to claim 1, characterized in that: The molar mass of the polyether polyol is between 2000 g / mol and 8000 g / mol; the polyether polyol comprises at least one of the following structural formulas:

3. The stretchable self-healing thermoplastic polyurethane adhesive according to claim 1, characterized in that: The isocyanate is an aromatic isocyanate; the aromatic isocyanate includes at least one of the following structural formulas:

4. The stretchable self-healing thermoplastic polyurethane adhesive according to claim 1, characterized in that: The chain extender includes at least one of the following structural formulas:

5. The stretchable self-healing thermoplastic polyurethane adhesive according to claim 1, characterized in that: The product is obtained by reacting the following raw materials in parts by weight: 79 parts of polyether polyol, 15 parts of isocyanate, and 6 parts of chain extender.

6. A method for preparing a stretchable self-healing thermoplastic polyurethane adhesive according to any one of claims 1 to 5, characterized in that: Includes steps: The polyether polyol and isocyanate are mixed and subjected to polymerization reaction to obtain a polymer precursor; The polymer precursor and the chain extender are heated and stirred to obtain a transparent colloid polyurethane material through a chain extension reaction; The transparent colloid polyurethane material is mixed with an organic solvent to obtain a thermoplastic polyurethane adhesive.

7. The method for preparing a stretchable self-healing thermoplastic polyurethane adhesive according to claim 6, characterized in that: The polymerization reaction temperature is 80° C.-100° C., and the polymerization reaction time is 2 h-22 h.

8. The method for preparing a stretchable self-healing thermoplastic polyurethane adhesive according to claim 6, characterized in that: The heating and stirring temperature is 80°C-100°C, and the heating and stirring time is 20min-30min; the chain extension reaction temperature is 120°C-130°C, and the chain extension reaction time is 8h-11h.

9. Use of the stretchable self-healing thermoplastic polyurethane adhesive according to any one of claims 1 to 5 in a supercapacitor or an electrochemical energy storage device.

10. The use according to claim 9, characterized in that: The electrode material in the electrochemical energy storage device includes a positive electrode active material or a negative electrode active material, and the thermoplastic polyurethane binder and the conductive agent; the mass ratio of the positive electrode active material or the negative electrode active material to the thermoplastic polyurethane binder and the conductive agent is (66.7-97.2):(2.8-25):(0-9.4).

Images