Functionalized carbon nanotube / polyurethane composite and method for preparing the same

Abstract

The application relates to a functionalized carbon nanotube / polyurethane composite material and a preparation method thereof, and belongs to the technical field of nanocomposites. First, dopamine and polyurethane chains are used to modify CNTs to obtain covalently and non-covalently modified functionalized carbon nanotubes CNTs-PDA-PU, then the functionalized carbon nanotubes CNTs-PDA-PU are added into a B component for synthesizing polyurethane, finally, the B component is mixed with an A component for synthesizing polyurethane and is cured, and finally, a functionalized carbon nanotube / polyurethane composite material with excellent mechanical and damping properties is obtained. The carbon nanotubes are modified by covalent and non-covalent combination to improve the interface interaction between the carbon nanotubes and the matrix, meanwhile, the preparation process of the composite material is optimized to improve the dispersibility of the CNTs in the matrix, so that multistage hydrogen bond and chemical bond action between the CNTs and the polyurethane matrix is realized, and after the covalent and non-covalent modification of the carbon nanotubes, the mechanical and damping properties of the polyurethane elastomer can be significantly improved.

Description

Technical Field

[0001] This invention relates to a functionalized carbon nanotube / polyurethane composite material and its preparation method, belonging to the field of nanocomposite materials technology. Background Technology

[0002] Polyurethane elastomers are widely used in many fields such as foams, plastics, coatings, adhesives, and damping pads due to their excellent wear resistance, thermal stability, elasticity, damping, and good biocompatibility. To expand their application capabilities, it is necessary to further improve the mechanical and damping properties of polyurethane elastomers. Adding nanofillers can significantly enhance the overall performance of polyurethane elastomers. Among them, carbon nanotubes (CNTs) are an excellent nanofiller with remarkable mechanical, optical, and electrical properties. However, due to their large specific surface area and high surface energy, CNTs are prone to agglomeration in polymers, resulting in poor dispersibility. The dispersion and interfacial interactions of CNTs are key factors affecting the performance of polymer composites. Functionalizing CNTs can improve their compatibility with the matrix and their dispersibility. Currently, covalent or non-covalent methods are generally used to functionalize CNTs, but covalent modification can destroy the CNT structure; non-covalent modification results in weak and unstable interfacial interactions. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a functionalized carbon nanotube / polyurethane composite material and its preparation method. First, CNTs are modified with dopamine and polyurethane chains to obtain covalently and non-covalently modified functionalized carbon nanotubes CNTs-PDA-PU. Then, these are added to component B of the synthesized polyurethane, and finally mixed with component A of the synthesized polyurethane and cured, ultimately yielding a functionalized carbon nanotube / polyurethane composite material with excellent mechanical and damping properties. Modifying carbon nanotubes through a combination of covalent and non-covalent modifications enhances their interfacial interaction with the matrix. Simultaneously, optimizing the composite material preparation process improves the dispersion of CNTs in the matrix, thereby achieving multi-level hydrogen bonding and chemical bonding between CNTs and the polyurethane matrix. The covalent and non-covalent modification of carbon nanotubes significantly improves the mechanical and damping properties of the polyurethane elastomer.

[0004] The objective of this invention is achieved through the following technical solutions.

[0005] A functionalized carbon nanotube / polyurethane composite material, wherein the composite material is obtained by curing component A and component B, and the composite material has a tensile strength greater than or equal to 30 MPa, an elongation at break greater than or equal to 500%, an elastic modulus greater than or equal to 2 MPa, and a damping temperature range tanδ ≥ 0.3.

[0006] Component B is a -NCO-terminated prepolymer formed by the reaction of functionalized carbon nanotubes (CNTs)-PDA-PU, polytetrahydrofuran ether diol, and diisocyanate.

[0007] The functionalized carbon nanotubes are obtained by sequentially modifying carbon nanotubes with dopamine and p-toluene diisocyanate (TDI) to obtain functionalized CNTs-PDA-TDI, and then reacting CNTs-PDA-TDI, polytetrahydrofuran ether diol and diisocyanate to obtain functionalized carbon nanotubes CNTs-PDA-PU.

[0008] Component A is a mixture of polyol, chain extender, catalyst, and defoamer; the polyol is polytetrahydrofuran ether diol and / or polyoxypropylene triol (330N); the chain extender is one or more of 1,4-butanediol (BDO), 1,2-ethylenediol, 1,6-hexanediol, 4,4'-methylenebis(2-chloroaniline) (MOCA), and E-300; the catalyst is dibutyltin dilaurate (T-12) and / or stannous octoate (T-9).

[0009] The mass of the functionalized carbon nanotubes is 0.01% to 0.3% of the mass of the composite material;

[0010] The molar ratio of -OH groups in component A to -NCO groups in component B is 1:1.03 to 1:1.07.

[0011] Furthermore, the polytetrahydrofuran ether diol is PTMEG2000 or PTMEG1000.

[0012] Furthermore, component A is formulated by mixing polytetrahydrofuran ether diol (PTMEG2000) with a molecular weight of 2000, polypropylene triol (330N) with a molecular weight of 4950, 1,4-butanediol (BDO), defoamer of model X-313 from Guangzhou Detian New Materials Co., Ltd., and catalyst dibutyltin dilaurate (T-12). The mass fractions of each component in component A are as follows: PTMEG2000 70.8~80.1 parts, 330N 19.6~19.8 parts, BDO 7.3~7.4 parts, defoamer 1.8~2.0 parts, and catalyst T-12 0.00035~0.00042 parts.

[0013] Furthermore, in component B, the polytetrahydrofuran ether diol is PTMEG2000, the diisocyanate is MDI, and the mass ratio of MDI to PTMEG2000 is 0.80~0.83:1.

[0014] Furthermore, the molar ratio of -OH groups in component A to -NCO groups in component B is 1:1.045 to 1:1.055. The most preferred ratio is 1.05 (i.e., R=1.05).

[0015] The present invention discloses a method for preparing a functionalized carbon nanotube / polyurethane composite material, the method comprising the following steps:

[0016] (1) CNTs-COOH was dispersed in Tris-HCl buffer solution, and after ultrasonic dispersion was uniform, dopamine hydrochloride (DOA-HCl) was added and ultrasonic dispersion was continued for 15-20 min. Then the reaction was carried out for 20-24 h, filtered and dried to obtain CNTs-PDA.

[0017] (2) The CNTs-PDA was ultrasonically mixed with N,N-dimethylformamide (DMF), and then TDI and catalyst T-12 were added. The mixture was stirred at 60~65 °C for 10~11 h to obtain CNTs-PDA-TDI;

[0018] (3) Add polytetrahydrofuran ether diol and diisocyanate to the CNTs-PDA-TDI, react for 4-5 h at 80-85 °C under a nitrogen atmosphere, centrifuge and wash to obtain functionalized carbon nanotubes CNTs-PDA-PU;

[0019] (4) The functionalized carbon nanotubes CNTs-PDA-PU were added to acetone and ultrasonically dispersed for 1-1.5 h. Then, polytetrahydrofuran ether diol was added and ultrasonically dispersed for 1-1.5 h. The acetone was removed by rotary evaporation to obtain a uniformly dispersed polytetrahydrofuran ether diol / CNTs-PDA-PU dispersion.

[0020] (5) Add diisocyanate to the dispersion in step (4) and react at 80~85 °C for 4~5 h to obtain a prepolymer containing functionalized carbon nanotubes, which is component B;

[0021] (6) Mix component B with component A and mechanically stir for 20-25 s, vacuum degas for 8-10 min, then pour into a mold preheated to 70-75 ℃, cure at 70-75 ℃ for 1.5-2 h, and finally cure at room temperature for 10-14 d to obtain a functionalized carbon nanotube / polyurethane composite material.

[0022] Furthermore, in step (1), the ratio of CNTs-COOH, Tris-HCl buffer solution, and DOA-HCl is 0.3 g: 300~350 mL: 0.3~0.6 g, and the concentration of Tris-HCl buffer solution is 0.01 mol / L with pH=8.5.

[0023] Furthermore, in step (1), the drying temperature is 80~90 ℃ and the drying time is 12~15 h.

[0024] Furthermore, in step (2), the ratio of CNTs-PDA, DMF, TDI and catalyst T-12 is 0.5 g: 80~100 mL: 0.5~0.6 g: 25~30 μL.

[0025] Furthermore, in step (3), the mass ratio of the polytetrahydrofuran ether diol, diisocyanate and CNTs-PDA in step (2) is 6.1~6.2:5~5.1:0.5.

[0026] Beneficial effects:

[0027] (1) In this invention, dopamine is first used to modify carbon nanotubes. Polydopamine (PDA) will coat the surface of carbon nanotubes through non-covalent interactions such as hydrogen bonds and van der Waals forces, introducing a large number of phenolic hydroxyl and imine functional groups that can react with isocyanates into the carbon nanotubes. Therefore, by using PDA as a medium, polyurethane chains are introduced into the carbon nanotubes in a functionalization method, which increases the proportion of polyurethane chains grafted into the carbon nanotubes.

[0028] (2) Since the activity of phenolic hydroxyl groups is lower than that of primary hydroxyl groups in PTMEG2000, the reaction efficiency of phenolic hydroxyl groups in PDA with MDI will be relatively low under competition with PTMEG2000. If MDI and PTMEG2000 are directly used to covalently modify CNTs-PDA, the grafting rate will not be improved. Therefore, before introducing PTMEG2000, this application first introduces TDI onto the surface of CNTs-PDA to introduce -NCO groups on CNTs; then, PTMEG2000 and MDI are added, and the -NCO groups on TDI and MDI can react with PTMEG2000. The early introduction of TDI can improve the grafting ability of active groups on CNTs, achieve the best modification effect, and allow PU chains to be grafted onto CNTs while polycondensing. The remaining o-isocyanate groups in TDI react with PTMEG2000, which can improve the efficiency of grafting PU chains onto CNTs-PDA.

[0029] (3) The dispersion and compatibility of functionalized carbon nanotubes in polyurethane matrix are significantly improved because, on the one hand, the PDA layer in functionalized carbon nanotubes will form hydrogen bonds with the polyurethane matrix; on the other hand, the polyurethane chains in functionalized carbon nanotubes will react chemically with the matrix. The combined effect of the two reduces the incompatibility between carbon nanotubes and polyurethane matrix.

[0030] (4) Due to the multiple hydrogen bonds and chemical bonds formed between CNTs-PDA-PU and the polyurethane matrix, the uniformly dispersed CNTs-PDA-PU acts as a crosslinking agent in the matrix. Under external force, the modified layer of CNTs, PDA, and PU chains can complete multi-level stress transfer, uniformly disperse stress, effectively suppress crack propagation, and improve the strength and toughness of the nanocomposite material. The mechanical properties of the composite material are significantly improved; compared with the polyurethane matrix, the tensile strength is increased by 97%, and the elongation at break is increased by 25%.

[0031] (5) After adding CNTs, the phase separation degree decreases, the restriction of hard segments on the movement of soft segments decreases, and the chain entanglement degree of soft segments decreases, thus improving the migration ability of chain segments. The improvement in chain segment migration ability and the increase in frictional sliding between CNTs and the polyurethane matrix cause the damping temperature range (tanδ≥0.3) to shift slightly to a lower temperature. The covalent bonds and strong hydrogen bonds between CNTs-PDA-PU and PU can provide good load transfer and improve the interfacial slip capability. As the chain segments move, more hydrogen bond dissipation and interfacial friction occur, resulting in an increase in damping capability. Attached Figure Description

[0032] Figure 1 The stress-strain curve of the composite material described in the embodiment is shown.

[0033] Figure 2 The stress-strain curves of the composite materials described in Example 2 and the comparative example are shown.

[0034] Figure 3 The figure shows the damping characteristic curve of the composite material described in the example.

[0035] Figure 4 The damping characteristic curves of the materials described in Example 2 and the comparative example are shown. Detailed Implementation

[0036] The present invention will be further described below with reference to specific embodiments. Unless otherwise specified, the methods described are conventional methods, and the raw materials described are obtainable from publicly available commercial sources.

[0037] In the following examples or comparative examples, the water content of PTMEG2000, 330N and BDO is less than or equal to 500 ppm.

[0038] Example 1

[0039] (1) 0.3 g CNTs-COOH was dispersed in Tris-HCl buffer solution (0.01 mol / L, pH=8.5) and sonicated for 10 min. Then 0.6 g DOA-HCl was added and sonicated for 15 min, and the mixture was reacted at room temperature for 24 h. The mixture was washed and filtered several times with distilled water to remove impurities, and dried at 80 ℃ for 12 h to obtain functionalized CNTs-PDA.

[0040] (2) Mix 0.5 g CNTs-PDA with 80 mL DMF by ultrasonication for 1 h, then add 0.5 g TDI and 30 μL catalyst T-12, and stir at 60 °C for 10 h to obtain CNTs-PDA-TDI.

[0041] (3) Add 5 g MDI and 6.1 g PTMEG2000 to the system described in step (2), react at 80 °C under a nitrogen atmosphere for 4 h, and finally obtain functionalized CNTs-PDA-PU by centrifugation and repeated washing with DMF.

[0042] (4) Add 0.058 g of functionalized carbon nanotubes CNTs-PDA-PU to 100 ml of acetone and sonicate for 1 h. Then add 30.25 g of PTMEG2000 and sonicate for 1 h. Remove the solvent acetone by rotary evaporation to obtain a uniformly dispersed PTMEG2000 / CNTs-PDA-PU dispersion.

[0043] (5) Add 24.75 g MDI to the system described in step (4) and react at 80 °C for 4 h to obtain a prepolymer containing functionalized carbon nanotubes, namely component B.

[0044] (6) Dissolve 0.005 parts of catalyst T-12 in 250 parts of dehydrated 330N and dilute and mix evenly to obtain 330N containing catalyst; mix 70.9 parts of dehydrated PTMEG2000, 19.7 parts of 330N containing catalyst, 7.4 parts of dehydrated BDO and 1.9 parts of defoamer (defoamer of model X-313 from Guangzhou Detian New Materials Co., Ltd.) evenly to obtain component A.

[0045] (7) After the reaction was completed, the components A and B were mixed according to the molar ratio of -OH groups in component A to -NCO groups in component B of 1:1.05 (i.e., 53 parts of component A and 47 parts of component B were mixed) and stirred at 1700 rpm for 20 s. Then, the mixture was placed under vacuum degassing conditions of ≤0.09 MPa for 7 min. The mixture was then poured into a mold preheated to 70 ℃ and cured in an oven at 70 ℃ for 1.5 h. Finally, the mixture was post-cured at room temperature for 10 d to obtain a functionalized carbon nanotube / polyurethane composite material with excellent mechanical and damping properties, denoted as PU / CNTs-PDA-PU0.05%.

[0046] Example 2

[0047] (1) 0.3 g CNTs-COOH was dispersed in Tris-HCl buffer solution (0.01 mol / L, pH=8.5) and sonicated for 10 min. Then 0.6 g DOA-HCl was added and sonicated for 15 min, and the mixture was reacted at room temperature for 24 h. The mixture was washed and filtered several times with distilled water to remove impurities, and dried at 80 ℃ for 12 h to obtain functionalized CNTs-PDA.

[0048] (2) Mix 0.5 g CNTs-PDA with 80 mL DMF by ultrasonication for 1 h, then add 0.5 g TDI and 30 μL catalyst T-12, and stir at 60 °C for 10 h to obtain CNTs-PDA-TDI.

[0049] (3) Add 5 g MDI and 6.1 g PTMEG2000 to the system described in step (2), react at 80 °C under a nitrogen atmosphere for 4 h, and finally obtain functionalized CNTs-PDA-PU by centrifugation and repeated washing with DMF.

[0050] (4) 0.117 g of functionalized carbon nanotubes CNTs-PDA-PU was added to 100 mL of acetone and ultrasonically dispersed for 1 h. Then, 30.25 g of PTMEG2000 was added and ultrasonically dispersed for 1 h. The solvent acetone was removed by rotary evaporation to obtain a uniformly dispersed PTMEG2000 / CNTs-PDA-PU dispersion.

[0051] (5) Add 24.75 g MDI to the system described in step (4) and react at 80 °C for 4 h to obtain a prepolymer containing functionalized carbon nanotubes, namely component B.

[0052] (6) Dissolve 0.005 parts of catalyst T-12 in 250 parts of dehydrated 330N and dilute and mix evenly to obtain 330N containing catalyst; mix 70.9 parts of dehydrated PTMEG2000, 19.7 parts of 330N containing catalyst, 7.4 parts of dehydrated BDO and 1.9 parts of defoamer (defoamer of model X-313 from Guangzhou Detian New Materials Co., Ltd.) evenly to obtain component A.

[0053] (7) After the reaction was completed, the components A and B were mixed according to the molar ratio of -OH groups in component A to -NCO groups in component B of 1:1.05 (i.e., 53 parts of component A and 47 parts of component B were mixed) and stirred at 1700 rpm for 20 s. Then, the mixture was placed under vacuum degassing conditions of ≤0.09 MPa for 7 min. The mixture was then poured into a mold preheated to 70 ℃ and cured in an oven at 70 ℃ for 1.5 h. Finally, the mixture was post-cured at room temperature for 10 d to obtain a functionalized carbon nanotube / polyurethane composite material with excellent mechanical and damping properties, denoted as PU / CNTs-PDA-PU0.1%.

[0054] Example 3

[0055] (1) 0.3 g CNTs-COOH was dispersed in Tris-HCl buffer solution (0.01 mol / L, pH=8.5) and sonicated for 10 min. Then 0.6 g DOA-HCl was added and sonicated for 15 min, and the mixture was reacted at room temperature for 24 h. The mixture was washed and filtered several times with distilled water to remove impurities, and dried at 80 ℃ for 12 h to obtain functionalized CNTs-PDA.

[0056] (2) Mix 0.5 g CNTs-PDA with 80 mL DMF by ultrasonication for 1 h, then add 0.5 g TDI and 30 μL catalyst T-12, and stir at 60 °C for 10 h to obtain CNTs-PDA-TDI.

[0057] (3) Add 5 g MDI and 6.1 g PTMEG2000 to the system described in step (2), react at 80 °C under a nitrogen atmosphere for 4 h, and finally obtain functionalized CNTs-PDA-PU by centrifugation and repeated washing with DMF.

[0058] (4) 0.351 g of functionalized carbon nanotubes CNTs-PDA-PU were added to 100 mL of acetone and ultrasonically dispersed for 1 h. Then, 30.25 g of PTMEG2000 was added and ultrasonically dispersed for 1 h. The solvent acetone was then removed by rotary evaporation to obtain a uniformly dispersed PTMEG2000 / CNTs-PDA-PU dispersion.

[0059] (5) Add 24.75 g MDI to the system described in step (4) and react at 80 °C for 4 h to obtain a prepolymer containing functionalized carbon nanotubes, namely component B.

[0060] (6) Dissolve 0.005 parts of catalyst T-12 in 250 parts of dehydrated 330N and dilute and mix evenly to obtain 330N containing catalyst; mix 70.9 parts of dehydrated PTMEG2000, 19.7 parts of 330N containing catalyst, 7.4 parts of dehydrated BDO and 1.9 parts of defoamer (defoamer of model X-313 from Guangzhou Detian New Materials Co., Ltd.) evenly to obtain component A.

[0061] (7) After the reaction was completed, the components A and B were mixed according to the molar ratio of -OH groups in component A to -NCO groups in component B of 1:1.05 (i.e., 53 parts of component A and 47 parts of component B were mixed) and stirred at 1700 rpm for 20 s. Then, the mixture was placed under vacuum degassing conditions of ≤0.09 MPa for 7 min. The mixture was then poured into a mold preheated to 70 ℃ and cured in an oven at 70 ℃ for 1.5 h. Finally, the mixture was post-cured at room temperature for 10 d to obtain a functionalized carbon nanotube / polyurethane composite material with excellent mechanical and damping properties, denoted as PU / CNTs-PDA-PU0.3%.

[0062] Comparative Example 1

[0063] (1) 30.25 g PTMEG2000 and 24.75 g MDI were reacted at 80 °C for 4 h to obtain the prepolymer, i.e. component B.

[0064] (2) Dissolve 0.005 parts of catalyst T-12 in 250 parts of dehydrated 330N and dilute and mix evenly to obtain 330N containing catalyst; mix 70.9 parts of dehydrated PTMEG2000, 19.7 parts of 330N containing catalyst, 7.4 parts of dehydrated BDO and 1.9 parts of defoamer (defoamer of model X-313 from Guangzhou Detian New Materials Co., Ltd.) evenly to obtain component A.

[0065] (3) Mix components A and B according to the molar ratio of -OH groups in component A to -NCO groups in component B of 1:1.05 (i.e., mix 53 parts of component A with 47 parts of component B), stir at 1700 rpm for 20 s, then place under vacuum degassing conditions of ≤0.09 MPa for 7 min, then pour into a mold preheated to 70 ℃, cure in an oven at 70 ℃ for 1.5 h, and finally cure at room temperature for 10 d to obtain polyurethane matrix material, denoted as Neat PU.

[0066] Comparative Example 2

[0067] To better illustrate the superior mechanical and damping properties of polyurethane composites prepared by co-modifying carbon nanotubes with dopamine and polyurethane chains, a PU / CNTs-COOH composite with a CNTs-COOH content of 0.1% was prepared as a comparison. The specific steps were as follows:

[0068] (1) 0.117 g CNTs-COOH was added to 100 ml of acetone and ultrasonically dispersed for 1 h. Then, 30.25 g PTMEG2000 was added and ultrasonically dispersed for 1 h. The solvent acetone was removed by rotary evaporation to obtain a uniformly dispersed PTMEG2000 / CNTs-COOH dispersion.

[0069] (2) Add 24.75 g MDI to the system described in step (1) and react at 80 °C for 4 h to obtain the prepolymer of CNTs-COOH participating in the reaction, namely component B.

[0070] (3) Dissolve 0.005 parts of catalyst in 250 parts of dehydrated 330N and dilute and mix evenly to obtain 330N containing catalyst; mix 70.9 parts of dehydrated PTMEG2000, 19.7 parts of 330N containing catalyst, 7.4 parts of dehydrated BDO and 1.9 parts of defoamer evenly to obtain component A.

[0071] (4) After the reaction is completed, the components A and B are mixed according to the molar ratio of -OH groups in component A to -NCO groups in component B of 1:1.05 (i.e., 53 parts of component A and 47 parts of component B are mixed) and stirred at 1700 rpm for 20 s. Then, the mixture is placed under vacuum degassing conditions of ≤0.09 MPa for 7 min. The mixture is then poured into a mold preheated to 70 ℃ and cured in an oven at 70 ℃ for 1.5 h. Finally, the mixture is post-cured at room temperature for 10 d to obtain the carbon nanotube / polyurethane composite material, denoted as PU / CNTs0.1%.

[0072] Comparative Example 3

[0073] To better illustrate the superior mechanical and damping properties of polyurethane composites prepared by co-modifying carbon nanotubes with dopamine and polyurethane chains, a PU / CNTs-PDA composite with a CNTs-PDA content of 0.1% was prepared as a comparison. The specific steps were as follows:

[0074] (1) 0.3 g CNTs-PDA was dispersed in Tris-HCl buffer solution (0.01 mol / L, pH=8.5) and sonicated for 10 min. Then 0.6 g DOA-HCl was added and sonicated for 15 min, and the mixture was reacted at room temperature for 24 h. The mixture was washed and filtered several times with distilled water to remove impurities, and dried at 80 ℃ for 12 h to obtain functionalized CNTs-PDA.

[0075] (2) 0.117 g CNTs-PDA was added to 100 mL of acetone and ultrasonically dispersed for 1 h. Then, 30.25 g PTMEG2000 was added and ultrasonically dispersed for 1 h. The solvent acetone was removed by rotary evaporation to obtain a uniformly dispersed PTMEG2000 / CNTs-PDA dispersion.

[0076] (3) Add 24.75 g MDI to the system described in step (2) and react at 80 °C for 4 h to obtain the prepolymer of CNTs-PDA participating in the reaction, namely component B.

[0077] (4) Dissolve 0.005 parts of catalyst in 250 parts of dehydrated 330N and dilute and mix evenly to obtain 330N containing catalyst; mix 70.9 parts of dehydrated PTMEG2000, 19.7 parts of 330N containing catalyst, 7.4 parts of dehydrated BDO and 1.9 parts of defoamer evenly to obtain component A.

[0078] (5) After the reaction is completed, the components A and B are mixed according to the molar ratio of -OH groups in component A to -NCO groups in component B of 1:1.05 (i.e., 53 parts of component A and 47 parts of component B are mixed) and stirred at 1700 rpm for 20 s. Then, the mixture is placed under vacuum degassing conditions of ≤0.09 MPa for 7 min. The mixture is then poured into a mold preheated to 70 ℃ and cured in a 70 ℃ oven for 1.5 h. Finally, the mixture is post-cured at room temperature for 10 d to obtain the carbon nanotube / polyurethane composite material, denoted as PU / CNTs-PDA0.1%.

[0079] Comparative Example 4

[0080] To better illustrate the superior mechanical and damping properties of polyurethane composites prepared by co-modifying carbon nanotubes with dopamine and polyurethane chains, a PU / CNTs-PU composite with a CNTs-PU content of 0.1% modified solely with polyurethane chains was prepared as a comparison. The specific steps were as follows:

[0081] (1) Mix 0.5 g CNTs-COOH with 80 mL DMF by ultrasonication for 1 h, then add 0.5 g TDI and 30 μL catalyst T-12, and stir at 60 °C for 10 h to obtain CNTs-TDI.

[0082] (2) Add 5 g MDI and 6.1 g PTMEG2000 to the system described in step (1), react at 80 °C under a nitrogen atmosphere for 4 h, and finally obtain functionalized CNTs-PU by centrifugation and repeated washing with DMF.

[0083] (3) Add 0.117 g CNTs-PU to 100 mL of acetone and sonicate for 1 h. Then add 30.25 g PTMEG2000 and sonicate for 1 h. Remove the solvent acetone by rotary evaporation to obtain a uniformly dispersed PTMEG2000 / CNTs-PU dispersion.

[0084] (4) Add 24.75 g MDI to the system described in step (3) and react at 80 °C for 4 h to obtain the prepolymer of CNTs-PU participating in the reaction, namely component B.

[0085] (5) Dissolve 0.005 parts of catalyst in 250 parts of dehydrated 330N and dilute and mix evenly to obtain 330N containing catalyst; mix 70.9 parts of dehydrated PTMEG2000, 19.7 parts of 330N containing catalyst, 7.4 parts of dehydrated BDO and 1.9 parts of defoamer evenly to obtain component A.

[0086] (6) After the reaction is completed, the components A and B are mixed according to the molar ratio of -OH groups in component A to -NCO groups in component B of 1:1.05 (i.e., 53 parts of component A and 47 parts of component B are mixed) and stirred at 1700 rpm for 20s. Then, the mixture is placed under vacuum degassing conditions of ≤0.09 MPa for 7 min. The mixture is then poured into a mold preheated to 70 ℃ and cured in an oven at 70 ℃ for 1.5 h. Finally, the mixture is post-cured at room temperature for 10 d to obtain the carbon nanotube / polyurethane composite material, denoted as PU / CNTs-PU0.1%.

[0087] The mechanical properties of each example and comparative example were tested according to GB / T1040.3-2006. The damping performance of the prepared materials was characterized using a dynamic thermomechanical analyzer (DMA). The test was conducted in shear mode at a frequency of 10 Hz, with a test temperature range of -80 to 120 °C and a heating rate of 3 °C / min. The damping performance was characterized by the damping factor (Tanδ) and the damping temperature range (tanδ ≥ 0.3). Based on the mechanical and damping properties of the carbon nanotube / polyurethane composites prepared in Examples 1-3 and Comparative Examples 1-3, it can be seen that the composites exhibit improved mechanical and damping properties compared to the polyurethane matrix. Combined with the comparative examples, it can be seen that, at the same content, the PU / CNTs-PDA-PU composite material exhibits the best mechanical and damping properties. Figure 1 and Figure 3 It can be seen that the composite material exhibits the best mechanical and damping properties when the CNTs-PDA-PU content is 0.1%.

[0088] Table 1

[0089]

[0090] This invention utilizes dopamine and polyurethane chains to modify CNTs, resulting in covalently and non-covalently modified functionalized carbon nanotubes (CNTs-PDA-PU). This increases the proportion of polyurethane links grafted onto the carbon nanotubes, significantly improving their dispersion and compatibility within the polyurethane matrix. Multiple hydrogen and chemical bonds enable the composite material to achieve multi-level stress transfer under external forces, uniformly dispersing stress and improving the mechanical properties of the nanocomposite. The frictional sliding between the functionalized CNTs and the polyurethane matrix, along with the excellent load transfer provided by covalent and strong hydrogen bonds, enhances interfacial slip capability, leading to greater hydrogen bond dissipation and interfacial friction, thus increasing damping capacity.

[0091] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A functionalized carbon nanotube / polyurethane composite material, characterized in that: The composite material is obtained by curing and molding component A and component B. The composite material has a tensile strength greater than or equal to 30 MPa, an elongation at break greater than or equal to 500%, an elastic modulus greater than or equal to 2 MPa, and a damping temperature range tanδ ≥ 0.

3. Component B is an -NCO-terminated prepolymer formed by the reaction of functionalized carbon nanotubes (CNTs)-PDA-PU, PTMEG2000, and MDI; the mass ratio of MDI to PTMEG2000 is 0.80~0.83:

1. The functionalized carbon nanotubes are obtained by modifying carbon nanotubes with dopamine and TDI in sequence to obtain functionalized CNTs-PDA-TDI, and then reacting CNTs-PDA-TDI, PTMEG2000 and MDI to obtain functionalized carbon nanotubes CNTs-PDA-PU; the functionalized carbon nanotubes are prepared by the following method, the steps of which include: (1) dispersing CNTs-COOH in Tris-HCl buffer solution, ultrasonically dispersing evenly, adding DOA-HCl and continuing ultrasonic dispersion for 15~20 min, then reacting for 20~24 h, filtering and drying to obtain CNTs-PDA; (2) ultrasonically mixing the CNTs-PDA with DMF, then adding TDI and catalyst T-12, stirring and reacting at 60~65 ℃ for 10~11 h to obtain CNTs-PDA-TDI; (3) adding PTMEG2000 and MDI to the CNTs-PDA-TDI, and reacting at 80~85 ℃ under a nitrogen atmosphere for 4~5 h. h, centrifugation and washing yielded functionalized carbon nanotubes CNTs-PDA-PU; Component A is a mixture of polyol, chain extender, catalyst and defoamer; the polyol is polytetrahydrofuran ether diol and / or 330N; the chain extender is one or more of BDO, 1,2-ethylene glycol, 1,6-hexanediol, MOCA and E-300; the catalyst is T-12 and / or T-9. The mass of the functionalized carbon nanotubes is 0.01% to 0.3% of the mass of the composite material; The molar ratio of -OH groups in component A to -NCO groups in component B is 1:1.03 to 1:1.

07.

2. The functionalized carbon nanotube / polyurethane composite material as described in claim 1, characterized in that: Component A is formulated by mixing PTMEG2000, 330N with a molecular weight of 4950, BDO, defoamer X-313 from Guangzhou Detian New Materials Co., Ltd., and T-12. The mass percentages of each component in Component A are as follows: PTMEG2000 70.8~80.1 parts, 330N 19.6~19.8 parts, BDO 7.3~7.4 parts, defoamer 1.8~2.0 parts, and catalyst T-12 0.00035~0.00042 parts.

3. The functionalized carbon nanotube / polyurethane composite material as described in claim 1, characterized in that: The molar ratio of -OH groups in component A to -NCO groups in component B is 1:1.045 to 1:1.

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4. A method for preparing the functionalized carbon nanotube / polyurethane composite material as described in any one of claims 1 to 3, characterized in that: The method steps include: (1) CNTs-COOH was dispersed in Tris-HCl buffer solution, and after being ultrasonically dispersed evenly, DOA-HCl was added and ultrasonically dispersed for 15-20 min. The mixture was then reacted for 20-24 h, filtered and dried to obtain CNTs-PDA. (2) The CNTs-PDA and DMF are ultrasonically mixed, and then TDI and catalyst T-12 are added. The mixture is stirred at 60~65 °C for 10~11 h to obtain CNTs-PDA-TDI; (3) Add PTMEG2000 and MDI to the CNTs-PDA-TDI, react for 4-5 h at 80-85 °C under a nitrogen atmosphere, centrifuge and wash to obtain functionalized carbon nanotubes CNTs-PDA-PU; (4) The functionalized carbon nanotubes CNTs-PDA-PU were added to acetone and ultrasonically dispersed for 1-1.5 h. Then PTMEG2000 was added and ultrasonically dispersed for 1-1.5 h. The acetone was removed by rotary evaporation to obtain a uniformly dispersed PTMEG2000 / CNTs-PDA-PU dispersion. (5) Add MDI to the dispersion in step (4) and react at 80~85 °C for 4~5 h to obtain a prepolymer containing functionalized carbon nanotubes, which is component B; (6) Mix component B with component A and mechanically stir for 20-25 s, vacuum degas for 8-10 min, then pour into a mold preheated to 70-75 ℃, cure at 70-75 ℃ for 1.5-2 h, and finally cure at room temperature for 10-14 d to obtain a functionalized carbon nanotube / polyurethane composite material.

5. The method for preparing a functionalized carbon nanotube / polyurethane composite material as described in claim 4, characterized in that: In step (1), the ratio of CNTs-COOH, Tris-HCl buffer solution, and DOA-HCl is 0.3 g: 300~350 mL: 0.3~0.6 g, and the concentration of Tris-HCl buffer solution is 0.01 mol / L with pH=8.

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6. The method for preparing a functionalized carbon nanotube / polyurethane composite material as described in claim 4, characterized in that: In step (1), the drying temperature is 80~90 ℃ and the drying time is 12~15 h.

7. The method for preparing a functionalized carbon nanotube / polyurethane composite material as described in claim 4, characterized in that: In step (2), the ratio of CNTs-PDA, DMF, TDI and catalyst T-12 is 0.5 g: 80~100 mL: 0.5~0.6 g: 25~30 μL.

8. The method for preparing a functionalized carbon nanotube / polyurethane composite material as described in claim 4, characterized in that: In step (3), the mass ratio of PTMEG2000, MDI and CNTs-PDA in step (2) is 6.1~6.2:5~5.1:0.5.

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