Preparation method of carbon nanotube and thermoplastic polyurethane composite tough fiber

Abstract

The invention provides a preparation method of a carbon nanotube and thermoplastic polyurethane composite tough fiber. The preparation method comprises the following steps: 1) synthesizing a superstrong polyurethane elastomer; (2) synthesizing a tannic acid and polyethyleneimine functionalized multi-walled carbon nanotube; (3) synthesizing a TA-PEI / MWCNTs / super-strong polyurethane spinning solution; (4) preparing a carbon nano tube and thermoplastic polyurethane composite tough fiber; tannic acid and polyethyleneimine functionalized multi-walled carbon nanotubes are used as a filler, TA molecules rich in phenolic hydroxyl groups are adsorbed on the walls of the carbon nanotubes through pi-pi interaction, and polyethyleneimine contains a large amount of amino groups, easily reacts with TA to form a cross-linked structure and shows relatively strong hydrophilicity, so that the solubility of the carbon nanotubes in a solvent is improved; and the adhesive force with a substrate is also improved. The nano-structure is introduced into TPU, so that reinforcement and toughening are realized, the strain exceeds 1200%, the breaking strength reaches 128.77 MPa, and the toughness exceeds 560 MJ / m < 3 >.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane composite fibers, and in particular relates to a method for preparing a carbon nanotube and thermoplastic polyurethane composite strong fiber. Background Art

[0002] Polyurethane elastic fiber is a block copolymer mainly composed of polyurethane, generally known as spandex, and is one of the most widely used elastic fibers. However, the mechanical properties of pure polyurethane fiber are poor and its application range is limited.

[0003] Carbon nanotubes are one-dimensional carbon nanomaterials with extremely high aspect ratios and excellent mechanical properties. They have great potential for application in the field of polyurethane composites. Carbon nanotubes can be imagined as cylinders formed by curling graphite sheets, usually with half a fullerene ball at the end. According to the manufacturing process, they can be divided into single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). SWCNTs are rolled up from a single graphite sheet, while MWCNTs are composed of two or more concentric cylindrical shells, with adjacent layers separated by about 0.34nm and having van der Waals forces. The aspect ratio of CNTs is generally greater than 1000, and its unique structure gives it unique properties, with electrical conductivity as high as 106S / cm and electron mobility of 105cm 2 / Vs, Young's modulus of 1.2TPa, about five times that of steel, tensile strength of 50-200GPa, excellent electrical, mechanical, thermal and other properties make carbon nanotubes recognized as ideal nanofillers. However, the agglomeration of carbon nanotubes and the poor interaction between carbon nanotubes and the matrix are two major problems restricting the large-scale application of CNTs / PU composites. Summary of the invention

[0004] In order to improve the strength and toughness of existing polyurethane fiber materials, the present invention proposes a method for preparing a composite strong fiber of carbon nanotubes and thermoplastic polyurethane. The present invention introduces tannic acid and polyethyleneimine functionalized multi-walled carbon nanotubes into the polyurethane elastomer. The addition of carbon nanotubes greatly improves the mechanical properties of the fiber.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for preparing a carbon nanotube and thermoplastic polyurethane composite strong fiber comprises the following steps:

[0007] 1) Synthesis of super strong polyurethane elastomer:

[0008] The polyether polyol is vacuumed and stirred to dehydrate at 100-120° C.; the polyether polyol, isocyanate and catalyst are then placed in a dry first solvent, and reacted at 60-80° C. in a nitrogen atmosphere to obtain a prepolymer solution; the prepolymer solution is then cooled, a chain extender and a second solvent are added, and the reaction is carried out at 40-60° C. in a nitrogen atmosphere; the obtained polymer solution is then transferred to a glass bottle and stored for further use;

[0009] 2) Synthesis of multi-walled carbon nanotubes functionalized with tannic acid and polyethyleneimine:

[0010] Dissolving tris(hydroxymethyl)aminomethane Tris in deionized water and adjusting the pH value to 8.5 to prepare a Tris buffer solution; then dissolving tannic acid and polyethyleneimine in the Tris buffer solution and mechanically stirring; then adding multi-walled carbon nanotubes, ultrasonically dispersing and stirring; then collecting the product by suction filtration, washing with deionized water and a first solvent, and drying at 40-60° C. to obtain tannic acid and polyethyleneimine functionalized multi-walled carbon nanotubes;

[0011] 3) Synthesis of TA-PEI / MWCNTs / super strong polyurethane spinning solution:

[0012] Ultrasonic dispersion of the tannic acid and polyethyleneimine functionalized multi-walled carbon nanotubes obtained in step 2) in the first solvent used in step 1); then slowly adding the solution to the polymer solution in step 1) to react at 60-80° C.; then vacuum degassing to obtain a spinning solution;

[0013] 4) Preparation of carbon nanotube and thermoplastic polyurethane composite tough fibers:

[0014] The spinning solution prepared in step 3) is sequentially subjected to wet spinning, coagulation bath coagulation, drawing, and winding to obtain a carbon nanotube and thermoplastic polyurethane composite strong fiber.

[0015] Preferably, in step 1), the polyether polyol is polytetrahydrofuran diol;

[0016] The molecular weight of the polyether polyol is 1000-3000;

[0017] The isocyanate is at least one of toluene diisocyanate TDI, isophorone diisocyanate IPDI, diphenylmethane diisocyanate MDI, and dicyclohexylmethane diisocyanate HMDI;

[0018] The chain extender is at least one of adipic acid dihydrazide ADH, oxalic acid dihydrazide ODH, dodecanedicarboxylic acid dihydrazide DDH, and isophthalic acid dihydrazide IPDH;

[0019] The catalyst is dibutyltin dilaurate;

[0020] The first solvent and the second solvent are at least one of anhydrous N, N-dimethylformamide DMF and anhydrous N, N-dimethylacetamide DMAc;

[0021] The molar ratio of the polyether polyol, isocyanate and chain extender is 1:(1.8-3.6):(0.5-2).

[0022] Preferably, in step 1), the polyether polyol is dehydrated by stirring under vacuum at 100-120° C. for 2-4 hours;

[0023] The mass concentration of the first solvent is 20%-40%, and the reaction is carried out at 60-80°C in a nitrogen atmosphere for 3-6 hours;

[0024] The mass concentration of the second solvent is 60%-80%, and the reaction is carried out at 40-60° C. in a nitrogen atmosphere for 12-15 hours.

[0025] Preferably, in step 2), the concentration of tris(hydroxymethyl)aminomethane is 5 mmol / L;

[0026] The mass ratio of tannic acid to polyethyleneimine is 1:(1-3), the solid content is 0.2 g / L, and mechanical stirring is performed at room temperature for 0.5-1 h;

[0027] The mass ratio of multi-walled carbon nanotubes to tannic acid is 3:1, and the mixture is ultrasonically dispersed for 1-4 hours and then stirred for 16-24 hours;

[0028] The length of multi-walled carbon nanotubes is 30-50 μm and the diameter is 8-15 nm.

[0029] Preferably, in step 3), ultrasonic dispersion is performed for 0.5-1h;

[0030] The mass ratio of multi-walled carbon nanotubes to super strong polyurethane elastomer is (0.2-2):100, and the reaction is carried out at 60-80°C for 8-12h;

[0031] The viscosity of the spinning solution is 30000-40000 mPa·s.

[0032] Preferably, in step 4), the spinning temperature is 20-40°C, the spinning rate is 50-150 m / min, the coagulation bath is deionized water, the coagulation time is 0.5-1h, the draft ratio is 150%-350%, and the drying temperature is 40-60°C.

[0033] Compared with the prior art, the present invention has the following advantages and technical effects:

[0034] (1) This application designs a new simple and easy method, using tannic acid and polyethyleneimine functionalized multi-walled carbon nanotubes as fillers, thermoplastic polyurethane as a matrix, and TA molecules rich in phenolic hydroxyl groups adsorbed on the wall of the carbon nanotubes through π-π interactions. TA can not only undergo a dopamine-like self-polymerization reaction to form aggregates and coat the surface of the multi-walled carbon nanotubes, but can also be oxidized under weak alkaline conditions to form quinones and react with amine groups through Michael addition or Schiff base reaction. The polyethyleneimine molecular structure contains a large number of amine groups, which are easy to react with TA to form a cross-linked structure, making the functionalized carbon nanotubes show strong hydrophilicity, which not only improves the solubility of the carbon nanotubes in the solvent, but also effectively improves the adhesion between the carbon nanotubes and the matrix.

[0035] (2) The polyurethane fiber obtained by the preparation method provided by the present invention has high strength and high toughness. The present invention introduces nanostructures into TPU, thereby achieving the strengthening and toughening effects of the material. The strain of the polyurethane fiber of the present invention exceeds 1200%, the breaking strength is as high as 128.77MPa, and the toughness exceeds 560MJ / m 3 . BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a synthetic route for super strong polyurethane elastomer SPU;

[0037] Figure 2 Schematic diagram of the synthesis of TA-PEI / MWCNTs / SPU composite strong fiber;

[0038] Figure 3 is the stress-strain curve of the carbon nanotube and thermoplastic polyurethane composite strong fiber in Example 1;

[0039] Figure 4 is the stress-strain curve of the polyurethane fiber in Comparative Example 1;

[0040] Figure 5 is the stress-strain curve of the carbon nanotube and thermoplastic polyurethane composite strong fiber in Comparative Example 2;

[0041] Figure 6 This is the stress-strain curve of the carbon nanotube and thermoplastic polyurethane composite strong fiber in Comparative Example 3. DETAILED DESCRIPTION

[0042] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of them. Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] The present application provides a method for preparing a carbon nanotube and thermoplastic polyurethane composite strong fiber, comprising the following steps:

[0044] The main raw materials include: filler: tannic acid and polyethyleneimine functionalized multi-walled carbon nanotubes; matrix: thermoplastic polyurethane;

[0045] 1) Synthesis of super strong polyurethane elastomer (SPU):

[0046] The polyether polyol is vacuum-stirred and dehydrated at 100-120° C. for 2-4 hours; the polyether polyol, isocyanate and catalyst are then placed in a dry first solvent, the mass concentration of the first solvent is 20%-40%, and reacted for 3-6 hours at 60-80° C. in a nitrogen atmosphere to obtain a prepolymer solution; the prepolymer solution is then cooled, a chain extender and a second solvent are added, the mass concentration of the second solvent is 60%-80%, and the reaction is carried out at 40-60° C. in a nitrogen atmosphere for 12-15 hours; the obtained polymer solution is then transferred to a glass bottle and stored for further use;

[0047] 2) Synthesis of TA-PEI / MWCNTs functionalized with tannic acid (TA) and polyethyleneimine (PEI):

[0048] Dissolve tris(hydroxymethyl)aminomethane (Tris) in deionized water and adjust the pH value to 8.5 to prepare a Tris buffer solution, wherein the concentration of tris(hydroxymethyl)aminomethane is 5 mmol / L; then dissolve tannic acid and polyethyleneimine in the Tris buffer solution in a mass ratio of 1:(1-3), wherein the solid content of the product obtained after dissolution is 0.2 g / L, and mechanical stirring is performed at room temperature for 0.5-1 h; then add multi-walled carbon nanotubes MWCNTs in a mass ratio of 3:1 to tannic acid TA, and stir for 16-24 h after ultrasonic dispersion for 1-4 h; then collect the product by suction filtration, wash with deionized water and a first solvent, and then dry at 40-60° C. to obtain TA-PEI / MWCNTs;

[0049] 3) Synthesis of TA-PEI / MWCNTs / super strong polyurethane spinning solution:

[0050] The TA-PEI / MWCNTs obtained in step 2) are ultrasonically dispersed in the first solvent used in step 1) for 0.5-1h; then the solution is slowly added to the polymer solution in step 1), the mass ratio of MWCNTs to SPU is (0.2-2):100, and the reaction is carried out at 60-80°C for 8-12h; then a spinning solution is obtained after vacuum degassing, and the viscosity is 30000-40000mPa·s;

[0051] 4) Preparation of carbon nanotube and thermoplastic polyurethane composite tough fibers:

[0052] The spinning solution prepared in step 3) is sequentially subjected to wet spinning, coagulation in a coagulation bath, drawing, and winding, and after completion, the carbon nanotube and thermoplastic polyurethane composite strong fiber is obtained;

[0053] The spinning temperature is 20-40°C, the spinning rate is 50-150 m / min, the coagulation bath is deionized water, the coagulation time is 0.5-1h, the draft ratio is 150%-350%, and the drying temperature is 40-60°C.

[0054] In one embodiment of the present application, in step 1), the polyether polyol is polytetrahydrofuran diol;

[0055] The molecular weight of the polyether polyol is 1000-3000;

[0056] The isocyanate is at least one of toluene diisocyanate TDI, isophorone diisocyanate IPDI, diphenylmethane diisocyanate MDI, and dicyclohexylmethane diisocyanate HMDI;

[0057] The chain extender is at least one of adipic acid dihydrazide ADH, oxalic acid dihydrazide ODH, dodecanedicarboxylic acid dihydrazide DDH, and isophthalic acid dihydrazide IPDH;

[0058] The catalyst is dibutyltin dilaurate;

[0059] The first solvent and the second solvent are at least one of anhydrous N, N-dimethylformamide DMF and anhydrous N, N-dimethylacetamide DMAc;

[0060] The molar ratio of the polyether polyol, isocyanate and chain extender is 1:(1.8-3.6):(0.5-2).

[0061] The tannic acid (TA) and polyethyleneimine (PEI) functionalized multi-walled carbon nanotubes of the present application greatly improve the strength and toughness of polyurethane compared to unmodified carbon nanotubes, wherein the chemical reaction principle or theoretical principle is: Figure 2As shown, TA molecules rich in phenolic hydroxyl groups are adsorbed on the carbon nanotube wall through π-π interactions, and TA undergoes a dopamine-like self-polymerization reaction to form aggregates, which are coated on the surface of multi-walled carbon nanotubes and oxidized to generate quinones under weak alkaline conditions, and react with amine groups through Michael addition or Schiff base reaction; while polyethyleneimine contains a large number of amine groups in its molecular structure, which are easy to react with TA to form a cross-linked structure, making the functionalized carbon nanotubes exhibit strong hydrophilicity, and functionalization can significantly increase the spatial repulsion between individual carbon nanotubes, thereby producing a stable dispersion and improving the solubility of carbon nanotubes in solvents; after functionalization, the multi-walled carbon nanotubes are rich in amino groups, which can react with isocyanate groups in the polyurethane matrix, effectively improving the adhesion between the carbon nanotubes and the matrix.

[0062] The reaction equations of the chemical reactions involved in the present invention include:

[0063]

[0064] c. Reaction of TA and PEI

[0065]

[0066] In this application, taking Example 1 as an example, the synthesis of super strong polyurethane (SPU) elastomer is as follows: Figure 1 As shown:

[0067] The terminal hydroxyl groups of the polyether polyol react with the isocyanate groups at 80°C in a nitrogen atmosphere to generate urea groups, and the reaction is continued for 3 hours to form a prepolymer solution;

[0068] The remaining isocyanate groups in the prepolymer react with the hydrazide groups of the chain extender under a nitrogen atmosphere at 40°C to generate acyl semicarbazide and carbamate groups;

[0069] The synthesis of TA-PEI / MWCNTs functionalized with tannic acid (TA) and polyethyleneimine (PEI) was Figure 2 As shown:

[0070] TA molecules rich in phenolic hydroxyl groups adsorb on the carbon nanotube wall through π-π interactions. TA undergoes a dopamine-like self-polymerization reaction to form aggregates, which are coated on the surface of multi-walled carbon nanotubes and oxidized to quinones under weak alkaline conditions, and react with amine groups through Michael addition or Schiff base reaction.

[0071] Synthesis of TA-PEI / MWCNTs / super strong polyurethane spinning solution Figure 2 As shown:

[0072] After functionalization, the multi-walled carbon nanotubes are rich in amine groups, which react with isocyanate groups in the polyurethane matrix to generate urea; the specific reaction equation involved is shown above.

[0073] The methods and devices not described in detail in the present invention are all prior art and will not be described in detail.

[0074] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0075] Example 1

[0076] A method for preparing a carbon nanotube / thermoplastic polyurethane composite strong fiber comprises the following steps:

[0077] 1) Synthesis of super strong polyurethane (SPU) elastomer:

[0078] The polyether polyol was dehydrated by stirring under vacuum at 120°C for 2 h;

[0079] The polyether polyol, isocyanate and catalyst are placed in a dry first solvent with a mass concentration of 20%, and reacted for 3 hours under a nitrogen atmosphere at 80° C. to obtain a prepolymer solution;

[0080] The prepolymer solution was cooled, and a chain extender and a second solvent were added, wherein the mass concentration of the second solvent was 80%, and the mixture was reacted at 40° C. under a nitrogen atmosphere for 15 hours;

[0081] The obtained polymer solution was transferred into a glass bottle and stored for further use;

[0082] 2) Synthesis of TA-PEI / MWCNTs functionalized with tannic acid (TA) and polyethyleneimine (PEI):

[0083] Dissolve tris(hydroxymethyl)aminomethane (Tris) in deionized water and adjust the pH to 8.5 to prepare a Tris buffer solution. The concentration of tris(hydroxymethyl)aminomethane is 5 mmol / L:

[0084] Dissolve tannic acid and polyethyleneimine in the above Tris buffer solution at a mass ratio of 1:1 and a solid content of 0.2 g / L, and mechanically stir at room temperature for 0.5 h;

[0085] MWCNTs were added at a mass ratio of 3:1 to TA, and ultrasonic dispersion was performed for 1 h followed by stirring for 24 h;

[0086] The product was collected by suction filtration, washed with deionized water and the first solvent, and dried at 60°C to obtain TA-PEI / MWCNTs;

[0087] 3) Synthesis of TA-PEI / MWCNTs / super strong polyurethane spinning solution:

[0088] Ultrasonic dispersion of the TA-PEI / MWCNTs obtained in step 2) in the first solvent used in step 1) for 1 h;

[0089] Slowly add the above solution into the polymer solution in step 1), the mass ratio of MWCNTs to SPU is 0.6:100, and react at 60°C for 8h;

[0090] After vacuum degassing, a spinning solution with a viscosity of 30000-40000 mPa·s is obtained;

[0091] 4) Preparation of carbon nanotube and thermoplastic polyurethane composite tough fibers:

[0092] The spinning solution of step 3) is subjected to wet spinning, coagulation in a coagulation bath, drawing, and winding to obtain the carbon nanotube and thermoplastic polyurethane composite strong fiber;

[0093] The spinning temperature was 25°C, the spinning rate was 50 m / min, the coagulation bath was deionized water, the coagulation time was 0.5 h, the draft ratio was 200%, and the drying temperature was 40°C;

[0094] The polyether polyol is polytetramethylene glycol with a molecular weight of 2000;

[0095] The chain extender is adipic acid dihydrazide;

[0096] The isocyanate is isophorone diisocyanate;

[0097] The molar ratio of polyether polyol to isocyanate to chain extender is 1:2.4:1.

[0098] Comparative Example 1

[0099] Thermoplastic polyurethane composite strong fiber includes the following steps:

[0100] (1) dehydrating the polyether polyol under vacuum stirring at 120° C. for 2 h;

[0101] (2) placing polyether polyol, isocyanate and catalyst in a dry solvent with a solvent mass concentration of 20%, reacting at 80° C. in a nitrogen atmosphere for 3 h to obtain a prepolymer solution;

[0102] (3) cooling the prepolymer solution, adding a chain extender and a solvent, wherein the solvent mass concentration is 80%, and reacting for 15 hours at 40° C. in a nitrogen atmosphere;

[0103] (4) subjecting the solution to wet spinning, coagulation in a coagulation bath, drawing and winding to obtain thermoplastic polyurethane fibers;

[0104] The spinning temperature was 25°C, the spinning rate was 50 m / min, the coagulation bath was deionized water, the coagulation time was 0.5 h, the draft ratio was 200%, and the drying temperature was 40°C;

[0105] The polyether polyol is polytetramethylene glycol with a molecular weight of 2000;

[0106] The chain extender is adipic acid dihydrazide;

[0107] The isocyanate is isophorone diisocyanate;

[0108] The molar ratio of polyether polyol to isocyanate to chain extender is 1:2.4:1.

[0109] Comparative Example 2

[0110] The difference from Example 1 is that the MWCNTs are not functionalized with tannic acid (TA) and polyethyleneimine (PEI).

[0111] Comparative Example 3

[0112] The difference from Example 1 is that the mass ratio of MWCNTs to SPU in step 3) is 1.6:100.

[0113] Performance Testing

[0114] The polyurethane fiber products obtained in Example and Comparative Examples 1-3 were subjected to mechanical property tests according to the following standards, and the results are shown in Table 1.

[0115] Mechanical properties: Data were provided by a universal material testing machine (Instron 5965), the test conditions were room temperature, -20% relative humidity, a tensile speed of 50 mm / min, and a tensile specimen length of 5 cm.

[0116] Table 1 Performance test data of polyurethane fibers of embodiments and comparative examples

[0117] Test items Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tensile strength(MPa) 128.77 68.56 61.09 92.35 Elongation at break (%) 1223.47 1001.16 1207.92 1191.1 <![CDATA[Toughness (MJ / m 3 )]]> 561.23 204.93 320.2 464.66

[0118] It can be seen from the test data in Table 1 that the carbon nanotube and thermoplastic polyurethane composite strong fiber of the present invention has achieved a strain of more than 1200%, a breaking strength of up to 128.77 MPa, and a toughness of more than 560 MJ / m 3 ;

[0119] By comparing Comparative Example 1 with Example 1, the introduction of tannic acid and polyethyleneimine functionalized multi-walled carbon nanotubes greatly improved the strength and toughness of polyurethane, wherein the tensile strength increased by 87.8% and the toughness increased by 173.9%;

[0120] By comparing Comparative Example 2 with Example 1, tannic acid (TA) and polyethyleneimine (PEI) functionalized multi-walled carbon nanotubes can be better dispersed in the matrix and interact with the matrix compared to unmodified carbon nanotubes, thereby improving the strength and toughness of the polyurethane;

[0121] Comparing Comparative Example 3 with Example 1, excessive carbon nanotubes will lead to reduced mechanical properties of the composite material because excessive carbon nanotubes will agglomerate and form defects.

[0122] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a carbon nanotube and thermoplastic polyurethane composite strong fiber, It is characterized in that The steps include: 1) Synthesis of super strong polyurethane elastomer: The polyether polyol is vacuumed and stirred to dehydrate at 100-120° C.; the polyether polyol, isocyanate and catalyst are then placed in a dry first solvent, and reacted at 60-80° C. in a nitrogen atmosphere to obtain a prepolymer solution; the prepolymer solution is then cooled, a chain extender and a second solvent are added, and the reaction is carried out at 40-60° C. in a nitrogen atmosphere; the obtained polymer solution is then transferred to a glass bottle and stored for further use; 2) Synthesis of multi-walled carbon nanotubes functionalized with tannic acid and polyethyleneimine: Dissolving tris(hydroxymethyl)aminomethane Tris in deionized water and adjusting the pH value to 8.5 to prepare a Tris buffer solution; then dissolving tannic acid and polyethyleneimine in the Tris buffer solution and mechanically stirring; then adding multi-walled carbon nanotubes, ultrasonically dispersing and stirring; then collecting the product by suction filtration, washing with deionized water and a first solvent, and drying at 40-60° C. to obtain tannic acid and polyethyleneimine functionalized multi-walled carbon nanotubes; 3) Synthesis of TA-PEI / MWCNTs / super strong polyurethane spinning solution: Ultrasonic dispersion of the tannic acid and polyethyleneimine functionalized multi-walled carbon nanotubes obtained in step 2) in the first solvent used in step 1); Then the solution is slowly added to the polymer solution of step 1) to react at 60-80°C; then the spinning solution is obtained after vacuum degassing; 4) Preparation of carbon nanotube and thermoplastic polyurethane composite tough fibers: The spinning solution prepared in step 3) is sequentially subjected to wet spinning, coagulation bath coagulation, drawing, and winding to obtain a carbon nanotube and thermoplastic polyurethane composite strong fiber.

2. The method for preparing the carbon nanotube and thermoplastic polyurethane composite strong fiber according to claim 1, It is characterized in that In step 1), the polyether polyol is polytetrahydrofuran diol; The molecular weight of the polyether polyol is 1000-3000; The isocyanate is at least one of toluene diisocyanate TDI, isophorone diisocyanate IPDI, diphenylmethane diisocyanate MDI, and dicyclohexylmethane diisocyanate HMDI; The chain extender is at least one of adipic acid dihydrazide ADH, oxalic acid dihydrazide ODH, dodecanedicarboxylic acid dihydrazide DDH, and isophthalic acid dihydrazide IPDH; The catalyst is dibutyltin dilaurate; The first solvent and the second solvent are at least one of anhydrous N,N-dimethylformamide DMF and anhydrous N,N-dimethylacetamide DMAc; The molar ratio of the polyether polyol, isocyanate and chain extender is 1:(1.8-3.6):(0.5-2).

3. The method for preparing the carbon nanotube and thermoplastic polyurethane composite strong fiber according to claim 1, It is characterized in that In step 1), the polyether polyol is dehydrated by stirring under vacuum at 100-120° C. for 2-4 hours; The mass concentration of the first solvent is 20%-40%, and the reaction is carried out at 60-80°C in a nitrogen atmosphere for 3-6 hours; The mass concentration of the second solvent is 60%-80%, and the reaction is carried out at 40-60° C. in a nitrogen atmosphere for 12-15 hours.

4. The method for preparing the carbon nanotube and thermoplastic polyurethane composite strong fiber according to claim 1, It is characterized in that In step 2), the concentration of tris(hydroxymethyl)aminomethane is 5 mmol / L; The mass ratio of tannic acid to polyethyleneimine is 1:(1-3), the solid content is 0.2 g / L, and mechanical stirring is performed at room temperature for 0.5-1 h; The mass ratio of multi-walled carbon nanotubes to tannic acid is 3:1, and the mixture is ultrasonically dispersed for 1-4 hours and then stirred for 16-24 hours; The length of multi-walled carbon nanotubes is 30-50 μm and the diameter is 8-15 nm.

5. The method for preparing the carbon nanotube and thermoplastic polyurethane composite strong fiber according to claim 1, It is characterized in that In step 3), ultrasonic dispersion is performed for 0.5-1 h; The mass ratio of multi-walled carbon nanotubes to super strong polyurethane elastomer is (0.2-2):100, and the reaction is carried out at 60-80°C for 8-12h; The viscosity of the spinning solution is 30000-40000 mPa·s.

6. The method for preparing the carbon nanotube and thermoplastic polyurethane composite strong fiber according to claim 1, It is characterized in that In step 4), the spinning temperature is 20-40°C, the spinning rate is 50-150 m / min, the coagulation bath is deionized water, the coagulation time is 0.5-1h, the draft ratio is 150%-350%, and the drying temperature is 40-60°C.

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