Conductive material based on TPU (thermoplastic polyurethane) composite carbon nanotubes as well as preparation method and application of conductive material

Abstract

The invention relates to the technical field of conductive materials, in particular to a conductive material based on TPU composite carbon nanotubes and a preparation method and application of the conductive material. Comprising the following raw materials in parts by mass: 70-78 parts of homogeneous TPU; 5 to 8 parts of multi-walled carbon nanotubes; 1 to 3 parts of aminated MXene; 2 to 5 parts of chopped carbon fiber; 0.5 to 2 parts of doped polyaniline; 0.3 to 1 part of zirconium phosphate nanosheets; 1 to 1.5 parts of ionic liquid [VBIM] Br; 1 to 2 parts of hydrophobic nano SiO2; 0.5 to 1 part of a silane coupling agent; 0.3 to 0.5 part of an antioxidant; and 0.5 to 1 part of zinc stearate. According to the preparation method, multi-element fillers such as the multi-walled carbon nanotubes, the aminated MXene, the short carbon fibers and the doped polyaniline are compounded, so that the broadband electromagnetic shielding effectiveness is improved, and the interfacial shear strength is improved.

Description

Technical Field

[0001] The invention relates to the technical field of conductive materials, in particular to a conductive material based on TPU composite carbon nanotubes and a preparation method and application thereof. Background Art

[0002] With the rapid development of intelligent transportation and aerospace technology, the integration and complexity of vehicle-mounted electronic systems are growing exponentially. Various precision sensors, high-frequency communication modules and autonomous driving controllers are densely deployed, resulting in an increasingly complex electromagnetic environment inside the vehicle. At the same time, aviation devices are iterating towards lightweight and multifunctionality. Composite materials account for more than 50% of the fuselage structure, but traditional metal-based electromagnetic protection layers are difficult to apply directly due to weight and compatibility issues. In this context, new conductive composite materials that are lightweight, highly flexible and have broadband electromagnetic shielding performance have become an industry necessity.

[0003] Thermoplastic polyurethane (TPU) has become an ideal choice for matrix preparation due to its excellent elasticity, wear resistance and processability. However, a single TPU matrix lacks electrical conductivity and requires the introduction of fillers to build a conductive network. Although traditional carbon fillers (such as carbon nanotubes and carbon fibers) can give materials conductive properties, they face multiple technical bottlenecks: Low efficiency in constructing a conductive network: Carbon nanotubes tend to form aggregates due to their high aspect ratio, and have poor dispersion uniformity in the TPU matrix, resulting in a broken conductive path at low frequencies (<1GHz), and shielding effectiveness (SE) is usually less than 40dB. When a single carbon nanotube is filled, it must exceed 10% by mass to form an effective percolation threshold, significantly increasing material density and cost.

[0004] Interface compatibility defects: The surface of carbon material is highly inert and is only physically entangled with the TPU matrix, and the interface shear strength is less than 15MPa. Under dynamic loads such as vibration and impact, the filler is prone to slip or debonding, resulting in a sudden drop in mechanical properties (such as elongation at break from 400% to less than 250%).

[0005] Insufficient environmental tolerance: The ester groups in the TPU molecular chain are easily corroded by the hot and humid environment and hydrolyzed, resulting in the attenuation of the mechanical properties of the matrix; the surface resistance of the carbon filler increases under long-term oxidation, and the annual attenuation rate of shielding effectiveness can reach 15%-20%. Although traditional silane coupling agent modification can improve interface bonding, the modified layer is easy to fall off and fail in extreme environments such as salt spray and ultraviolet light.

[0006] Chinese patent application CN111171280A, published on July 27, 2021, discloses a method for preparing a conductive and thermally conductive functionalized carbon nanotube / TPU composite material. First, functionalized carbon nanotubes (CS-CNT) are obtained by modifying functionalized carbon nanotubes with chitosan, which are reacted with 4,4'-diphenylmethane diisocyanate, and then polytetramethylene ether glycol, 1,4-butanediol and a catalyst are added to synthesize the conductive and thermally conductive functionalized carbon nanotube / TPU composite material through prepolymerization-chain extension reaction. Although it attempts to improve the conductivity by compounding multiple fillers, it still has a lot of room for improvement in electromagnetic shielding and mechanical properties. Summary of the invention

[0007] In view of the above deficiencies in the prior art, the purpose of the present invention is to provide a conductive material based on TPU composite carbon nanotubes, by compounding multi-fillers such as multi-walled carbon nanotubes, amino-modified MXene, chopped carbon fibers, doped polyaniline, etc., to construct a "1D long-range conductive network + 2D interface polarization absorption + 3D stress dispersion skeleton" synergistic system to achieve improved broadband electromagnetic shielding effectiveness and improved interface shear strength.

[0008] Another object of the present invention is to provide a method for preparing a conductive material based on TPU composite carbon nanotubes, which adopts multi-stage melt blending to directional construct a conductive network, gradient hot pressing-quenching to form a filler concentration gradient, plasma activation-in-situ amination to enhance interface bonding and PVD coating to improve surface properties, so as to solve the problems of uneven filler dispersion, weak interface bonding and poor environmental stability.

[0009] Another three objectives of the present invention are to provide an application of a conductive material based on TPU composite carbon nanotubes for use in the field of anti-interference of vehicle-mounted electronic equipment or in the field of electromagnetic protection of aircraft composite materials.

[0010] The present invention is achieved by adopting the following technical solutions: The conductive material based on TPU composite carbon nanotubes comprises the following raw materials in parts by weight: homogeneous TPU: 70-78 parts; multi-walled carbon nanotubes: 5-8 parts; amino MXene: 1-3 parts; short-cut carbon fibers: 2-5 parts; doped polyaniline: 0.5-2 parts; zirconium phosphate nanosheets: 0.3-1 parts; ionic liquid [VBIM] Br: 1-1.5 parts; hydrophobic nano-SiO 2 : 1-2 parts; silane coupling agent: 0.5-1 parts; antioxidant: 0.3-0.5 parts; zinc stearate: 0.5-1 parts.

[0011] The length of the chopped carbon fiber is 3-5 mm, the silane coupling agent is KH550, and the antioxidant is 1076.

[0012] Preparation method of doped polyaniline (PANI): 10g of intrinsic PANI powder was added to 200mL of dopant solution (1M HCl) and magnetically stirred for 30min to fully wet it. Transferred to an ultrasonic reactor and ultrasonically treated at 40kHz and 500W for 2h to promote the embedding of acid molecules into the PANI main chain. The mixture was filtered and washed with deionized water until the filtrate pH was neutral. Vacuum dried (60℃, 12h) to obtain doped PANI powder.

[0013] Hydrophobic Nano-SiO 2 When adding, surface modification is required. The specific method is: 100gSiO 2 Add to 500 mL of ethanol and disperse by ultrasonication (40 kHz, 300 W) for 30 min to form a uniform suspension. Add 10 g of KH550 and reflux at 80 °C for 4 h to hydrolyze and condense KH550 and graft it onto SiO 2 Surface; centrifugation (8000rpm, 10min) to collect modified SiO 2 The unreacted KH550 was removed by washing with ethanol for 3 times; and the hydrophobic nano-SiO 2 (Contact angle > 130°).

[0014] The preparation method of the homogeneous TPU comprises the following steps: Ⅰ. Dehydrate PTMG with a molecular weight of 2000 at 105-110°C in vacuum for 2-3 hours; cool to 85°C, add MDI and dibutyltin dilaurate, and mechanically stir at 200 rpm for 2.5-3 hours under nitrogen protection; Ⅱ. The product obtained in step Ⅰ is cooled to 75-80 ℃, and an ethylenediamine / epoxy monomer mixture and an anti-hydrolysis agent are added, followed by shear emulsification at 5000-5500 rpm for 10-20 min to force dispersion of the epoxy monomer and avoid local agglomeration; then poured into a polytetrafluoroethylene mold and aged at 110-115 ℃ for 4-5 h to obtain a homogeneous TPU.

[0015] The mass proportions of the raw materials are as follows: PTMG: 100 parts; MDI: 32-35 parts; ethylenediamine: 6-8 parts; epoxy monomer: 2-3 parts; dibutyltin dilaurate: 0.02-0.05 parts; anti-hydrolysis agent: 0.5-1 parts; the epoxy monomer is one of glycidyl methacrylate or glycidyl acrylate; the anti-hydrolysis agent is one of carbodiimide or polycarbodiimide.

[0016] The method for preparing the conductive material based on TPU composite carbon nanotubes comprises the following steps: (1) Each raw material is added to a twin-screw extruder in turn for multi-stage melt blending and granulation: in the feeding section at 150-160°C, pretreated homogeneous TPU and zinc stearate are added, and the feeding rate is controlled at 5-8 kg / h; in the melting section, at 170-180°C, the composite amino MXene and chopped carbon fibers, hybridized multi-walled carbon nanotubes and zirconium phosphate are introduced as fillers, and preliminary dispersion is achieved by rotating the screw at a medium speed of 200-300 rpm; in the mixing section, at 185-195°C, doped polyaniline, ionic liquid [VBIM]Br and silane coupling agent are simultaneously injected at 1200-1500 s -1 The directional construction and interface bonding of the conductive network are achieved under the action of the high shear zone; in the homogenization stage, at 175-180℃, nano-SiO 2 and antioxidant, and remove volatile components under vacuum conditions of -0.06~-0.08MPa to obtain pre-treated particles, with a melt pressure of 8-12MPa and a total residence time of 3.5-4.5min; (2) Placing the pretreated body particles in a mold and performing hot pressing-quenching treatment: preheating the pretreated body particles to 170-180°C and pressurizing to 2-4MPa; then performing a first-stage pressurization at 5-8MPa and 190-200°C, and keeping the temperature for 2-3min; then performing a second-stage pressurization at 10-15MPa and 200-205°C, using gradient temperature control: the temperature difference between the surface layer and the core layer is 15-20°C; then performing liquid nitrogen quenching, with a flow rate of 20-50L / min and a holding pressure of 10-12MPa; then cooling to below 80°C for demolding to obtain the pretreated body; (3) PVD coating is performed on the pre-treated body, and Al2O3 with a mass ratio of 7:3 is used for magnetron sputtering. 2 O 3 / TiO 2 Composite target, substrate temperature: 80-120°C, sputtering power: 200-300W, film thickness: 50-100nm, to obtain a conductive material based on TPU composite carbon nanotubes.

[0017] The pretreatment of the homogeneous TPU comprises the following steps: ① Plasma activation: The homogeneous TPU is treated with atmospheric pressure dielectric barrier discharge equipment, with a power density of 2.8-3.2W / cm², a processing speed of 2m / min, a residence time of 120s, and a TPU surface temperature of <50°C; ② In-situ amination strengthening: 8-12wt% of ethylenediamine is dissolved in a mixed solvent of ethanol / water with a volume ratio of 7:3, and 0.3-0.5% of polyether modified siloxane is added as a penetrant; then the product treated in step ① is added to the penetrant, and ultrasonically treated at 63-67°C for 2.5-3h. The endpoint is determined by the surface Zeta potential ≥+40mV, and the pretreated homogeneous TPU is obtained.

[0018] The method for compounding the aminated MXene and the chopped carbon fiber is as follows: firstly, the MXene is aminated, and then the aminated MXene is compounded with the chopped carbon fiber; The preparation method of amino MXene is as follows: 50gTi 3 AlC 2 The powder was slowly added to 200 mL HF and stirred magnetically (500 rpm) for 24 h at a reaction temperature of 25 °C. The precipitate was collected by centrifugation (10,000 rpm, 15 min), washed with deionized water until neutral (pH = 7), and freeze-dried to obtain multilayer Ti 3 C 2 T x (T=-OH / -F). 5gTi 3 C 2 T x Dispersed in 200 mL of ethylenediamine solution, reacted at 80 °C with magnetic stirring for 6 h. The product was collected by centrifugation (8000 rpm, 10 min), washed with ethanol three times, and dried under vacuum at 60 °C for 12 h to obtain amino MXene (surface-NH 2 Density>3groups / nm²).

[0019] MXene dispersion: Add the aminated MXene powder into deionized water and perform ultrasonic treatment in an ice bath: 40kHz, 500W, 20-60min; then immerse the chopped carbon fiber into the aminated MXene dispersion, vacuum filter, and vacuum dry at 40-60°C for 4-6h to obtain an aminated MXene / chopped carbon fiber composite.

[0020] The hybridization treatment method of multi-walled carbon nanotubes and zirconium phosphate is as follows: multi-walled carbon nanotubes and zirconium phosphate are taken at a mass ratio of 1: (0.2-0.5), and then subjected to hydrothermal treatment, reacting at a filling degree of 70-80% and 180-220° C. for 6-12 hours to obtain hybridized multi-walled carbon nanotubes-zirconium phosphate.

[0021] The application of the conductive material based on TPU composite carbon nanotubes is used in the field of anti-interference of vehicle-mounted electronic equipment or the field of electromagnetic protection of aircraft composite materials.

[0022] The working principle of the present invention is: Raw material synergy mechanism: Multi-walled carbon nanotubes (CNTs): 1D structure builds a long-range conductive network, which dominates the electromagnetic wave reflection loss (>50dB@1GHz). Aminated MXene: 2D sheets enhance absorption loss through interface polarization, surface -NH 2 Covalent bonding with TPU epoxy groups increases the interfacial shear strength to 28MPa. Chopped carbon fiber (CF): 3D skeleton disperses stress, impact strength>50kJ / m², and MXene-coated CF forms "line-surface" conductive synergy. Doped polyaniline (PANI): Protonic acid doping increases conductivity (1→10S / cm), forms a dynamic hydrogen bond network with ionic liquid [VBIM]Br, and adaptively adjusts resistance. Zirconium phosphate (ZrP) nanosheets: Intercalation blocks water and oxygen penetration, and the resistance change rate after wet heat aging is <10%.

[0023] Plasma activation + in-situ amination: generation of -NH on the surface of TPU 2 (XPS detected N content of 5.8%), forming an amide bond with CNTs-COOH, and the contact resistance is reduced to 0.07Ω·cm. Gradient hot pressing-quenching: The surface CNTs concentration is gradient distributed, and the broadband shielding performance is improved. PVD coating: Al 2 O 3 / TiO 2 The composite layer increases the surface hardness and improves the scratch resistance by 3 times.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention achieves broadband shielding effectiveness improvement through the synergistic effect of multiple fillers such as multi-walled carbon nanotubes (1D structure constructs a long-range conductive network, which dominates the electromagnetic wave reflection loss), amino MXene (2D sheets enhance absorption loss through interface polarization), and chopped carbon fibers (3D skeleton disperses stress and forms "line-surface" conductive synergy with MXene), combined with a gradient hot pressing process to form a conductive filler concentration gradient from the surface layer to the core layer. The average shielding effectiveness (SE) can reach 58.2-68.1dB, and the absorption loss accounts for up to 62%. It has both reflection and absorption loss mechanisms, solving the problem of insufficient low-frequency shielding effectiveness of traditional materials.

[0025] (2) Amination of -NH on the MXene surface 2The groups are covalently bonded with the epoxy groups in the TPU matrix, which improves the interface shear strength; the chopped carbon fibers form a 3D stress dispersion skeleton, with an impact strength of >50kJ / m² (up to 62kJ / m²), a tensile strength of 28.5-33.2MPa, and a bending strength of 45.2-53.6MPa. At the same time, the doped polyaniline and the ionic liquid [VBIM]Br form a dynamic hydrogen bond network, giving the material the ability to adaptively adjust resistance, making it less likely to undergo interface peeling under dynamic loads, and significantly better mechanical properties than unmodified traditional TPU-based composite materials.

[0026] (3) The intercalation structure of zirconium phosphate nanosheets effectively blocks water and oxygen penetration. After wet heat aging, the resistance change rate is <10% (minimum +5.5%), and the SE retention rate is >93.5%. 2 After surface modification, the contact angle is >140° (up to 155°). In addition, the material reaches UL94V-0, meeting the needs of long-term stable use in complex environments and solving the problem of performance degradation of traditional materials in environments such as humidity, heat, and salt spray.

[0027] (4) Through the compounding of multi-fillers such as multi-walled carbon nanotubes, amino-modified MXene, and chopped carbon fibers and the gradient hot pressing process, a "line-surface-body" multi-level conductive network is constructed. Combined with plasma activated interface modification and PVD coating technology, the volume resistivity is as low as 2.5×10²Ω·cm and the surface resistivity is as low as 3.1×10³Ω / sq. The resistance change rate after wet-heat aging is only +5.5%. The conductive performance is excellent and stable, meeting the application requirements in complex electromagnetic environments. DETAILED DESCRIPTION

[0028] In order to make the purpose and technical solution of the present invention more clear, the present invention is further described in detail below.

[0029] Manufacturer: Multi-walled carbon nanotubes: Jiangsu Tiannai Technology Co., Ltd.; MXene: Chongqing MXene Technology Co., Ltd. Ionic liquid [VBIM]Br: Sigma-Aldrich, USA.

[0030] In the embodiment, the pretreatment method of some raw materials is: Preparation method of doped polyaniline (PANI): 10g of intrinsic PANI powder was added to 200mL of dopant solution (1M HCl) and magnetically stirred for 30min to fully wet it. Transferred to an ultrasonic reactor and ultrasonically treated at 40kHz and 500W for 2h to promote the embedding of acid molecules into the PANI main chain. The mixture was filtered and washed with deionized water until the filtrate pH was neutral. Vacuum dried (60℃, 12h) to obtain doped PANI powder.

[0031] Hydrophobic Nano-SiO 2 When adding, surface modification is required. The specific method is: 100gSiO 2 Add to 500 mL of ethanol and disperse by ultrasonication (40 kHz, 300 W) for 30 min to form a uniform suspension. Add 10 g of KH550 and reflux at 80 °C for 4 h to hydrolyze and condense KH550 and graft it onto SiO 2 Surface; centrifugation (8000rpm, 10min) to collect modified SiO 2 The unreacted KH550 was removed by washing with ethanol for 3 times; and the hydrophobic nano-SiO 2 .

[0032] The preparation method of amino MXene is as follows: 50gTi 3 AlC 2 The powder was slowly added to 200 mL HF and stirred magnetically (500 rpm) for 24 h at a reaction temperature of 25 °C. The precipitate was collected by centrifugation (10,000 rpm, 15 min), washed with deionized water until neutral (pH = 7), and freeze-dried to obtain multilayer Ti 3 C 2 T x (T=-OH / -F). 5gTi 3 C 2 T x Dispersed in 200 mL of ethylenediamine solution, reacted at 80°C with magnetic stirring for 6 h. The product was collected by centrifugation (8000 rpm, 10 min), washed with ethanol three times, and dried under vacuum at 60°C for 12 h to obtain amino MXene.

[0033] Example 1 The conductive material based on TPU composite carbon nanotubes includes the following raw materials in parts by weight: homogeneous TPU: 70 parts; multi-walled carbon nanotubes: 5 parts; amino MXene: 1 part; short-cut carbon fiber: 2 parts; doped polyaniline: 0.5 parts; zirconium phosphate nanosheets: 0.3 parts; ionic liquid [VBIM] Br: 1 part; hydrophobic nano-SiO 2: 1 part; silane coupling agent: 0.5 part; antioxidant: 0.3 part; zinc stearate: 0.5 part. The length of the chopped carbon fiber is 3 mm, the silane coupling agent is KH550, and the antioxidant is 1076.

[0034] The preparation method of homogeneous TPU comprises the following steps: Ⅰ. Dehydrate PTMG with a molecular weight of 2000 at 105°C in vacuum for 2 hours; cool to 85°C, add MDI and dibutyltin dilaurate, and mechanically stir at 200 rpm for 2.5 hours under nitrogen protection; Ⅱ. The product obtained in step Ⅰ is cooled to 75℃, and the mixture of ethylenediamine / epoxy monomer and anti-hydrolysis agent are added, followed by shearing and emulsification at 5000rpm for 10min; poured into a polytetrafluoroethylene mold, and aged at 110℃ for 4h to obtain a homogeneous TPU. The mass fractions of each raw material are: PTMG: 100 parts; MDI: 32 parts; ethylenediamine: 6 parts; epoxy monomer: 2 parts; dibutyltin dilaurate: 0.02 parts; anti-hydrolysis agent: 0.5 parts; the epoxy monomer is glycidyl methacrylate; the anti-hydrolysis agent is carbodiimide.

[0035] The method for preparing the conductive material based on TPU composite carbon nanotubes comprises the following steps: (1) Each raw material was sequentially added into a twin-screw extruder for multi-stage melt blending and granulation: in the feeding section at 150°C, pretreated homogeneous TPU and zinc stearate were added, and the feeding rate was controlled at 5 kg / h; in the melting section, at 170°C, the composite amino MXene and chopped carbon fibers, hybridized multi-walled carbon nanotubes and zirconium phosphate were introduced as fillers, and preliminary dispersion was achieved by rotating the screw at a medium speed of 200 rpm; in the mixing section, at 185°C, doped polyaniline, ionic liquid [VBIM]Br and silane coupling agent were simultaneously injected, and the mixture was heated for 1200 s. -1 The directional construction and interface bonding of the conductive network are achieved under the action of the high shear zone; in the homogenization stage, at 175°C, nano-SiO 2 and antioxidant, and remove volatile components under -0.06MPa vacuum conditions to obtain pre-treated particles, with a melt pressure of 8MPa and a total material residence time of 3.5min; (2) Placing the pretreated body particles in a mold and performing hot pressing-quenching treatment: preheating the pretreated body particles to 170°C and pressurizing to 2MPa; then performing a first-stage pressurization at 5MPa and 190°C and keeping the temperature for 2min; then performing a second-stage pressurization at 10MPa and 200°C, using gradient temperature control: the temperature difference between the surface layer and the core layer is 15°C; then performing liquid nitrogen quenching, with a flow rate of 20L / min and a holding pressure of 10MPa; then cooling to below 80°C and demolding to obtain the pretreated body; (3) PVD coating is performed on the pre-treated body, and Al2O3 with a mass ratio of 7:3 is used for magnetron sputtering. 2 O 3 / TiO 2 Composite target, substrate temperature: 80°C, sputtering power: 200W, film thickness: 50nm, and a conductive material based on TPU composite carbon nanotubes was obtained.

[0036] The pretreatment of homogeneous TPU comprises the following steps: ① Plasma activation: The homogeneous TPU is treated with atmospheric pressure dielectric barrier discharge equipment, with a power density of 2.8W / cm², a processing speed of 2m / min, a residence time of 120s, and a TPU surface temperature of 48°C; ② In-situ amination strengthening: 8 wt% of ethylenediamine was dissolved in an ethanol / water mixed solvent with a volume ratio of 7:3, and 0.3% of polyether-modified siloxane was added as a penetrant; then the product treated in step ① was added to the penetrant, and ultrasonically treated at 63°C for 2.5h. The endpoint was determined by the surface Zeta potential of +40mV to obtain the pretreated homogeneous TPU.

[0037] The treatment method for the composite of aminated MXene and chopped carbon fiber is as follows: aminated MXene dispersion: the aminated MXene powder is added to deionized water and ultrasonically treated in an ice bath: 40kHz, 500W, 20min; then the chopped carbon fiber is immersed in the aminated MXene dispersion, vacuum filtered, and vacuum dried at 40°C for 4h to obtain an aminated MXene / chopped carbon fiber composite.

[0038] The hybridization treatment method of multi-walled carbon nanotubes and zirconium phosphate is as follows: multi-walled carbon nanotubes and zirconium phosphate are taken at a mass ratio of 1:0.2, and then subjected to hydrothermal treatment, reacted at 180°C for 6 hours at a filling degree of 70%, to obtain hybridized multi-walled carbon nanotubes-zirconium phosphate.

[0039] Conductive materials based on TPU composite carbon nanotubes are used in the field of anti-interference of vehicle-mounted electronic equipment.

[0040] Example 2 The conductive material based on TPU composite carbon nanotubes includes the following raw materials in parts by weight: homogeneous TPU: 75 parts; multi-walled carbon nanotubes: 6 parts; amino MXene: 2 parts; short-cut carbon fibers: 3 parts; doped polyaniline: 1 part; zirconium phosphate nanosheets: 0.5 parts; ionic liquid [VBIM] Br: 1.2 parts; hydrophobic nano-SiO 2 :1.5 parts; silane coupling agent: 0.8 parts; antioxidant: 0.4 parts; zinc stearate: 0.7 parts. The length of the chopped carbon fiber is 4 mm, the silane coupling agent is KH550, and the antioxidant is 1076.

[0041] The preparation method of homogeneous TPU comprises the following steps: Ⅰ. Dehydrate PTMG with a molecular weight of 2000 under vacuum at 108°C for 2 hours; cool to 85°C, add MDI and dibutyltin dilaurate, and mechanically stir at 200 rpm for 3 hours under nitrogen protection; Ⅱ. The product obtained in step Ⅰ was cooled to 78°C, and the mixture of ethylenediamine / epoxy monomer and anti-hydrolysis agent was added, followed by shearing and emulsification at 5300rpm for 15min; poured into a polytetrafluoroethylene mold, and aged at 113°C for 4h to obtain a homogeneous TPU. The mass fractions of each raw material are: PTMG: 100 parts; MDI: 34 parts; ethylenediamine: 7 parts; epoxy monomer: 2 parts; dibutyltin dilaurate: 0.03 parts; anti-hydrolysis agent: 0.8 parts; the epoxy monomer is glycidyl acrylate; the anti-hydrolysis agent is polycarbodiimide.

[0042] The method for preparing the conductive material based on TPU composite carbon nanotubes comprises the following steps: (1) Each raw material was sequentially added into a twin-screw extruder for multi-stage melt blending and granulation: in the feeding section at 155°C, pretreated homogeneous TPU and zinc stearate were added, and the feeding rate was controlled at 7kg / h; in the melting section, at 175°C, the composite amino MXene and chopped carbon fibers, hybridized multi-walled carbon nanotubes and zirconium phosphate were introduced as fillers, and preliminary dispersion was achieved by rotating the screw at a medium speed of 250rpm; in the mixing section, at 190°C, doped polyaniline, ionic liquid [VBIM]Br and silane coupling agent were simultaneously injected at 1350s -1 The directional construction and interface bonding of the conductive network are achieved under the action of the high shear zone; in the homogenization stage, at 178 ° C, nano-SiO 2 and antioxidant, and remove volatile components under -0.07MPa vacuum conditions to obtain pre-treated particles, the whole melt pressure is 10MPa, and the total material residence time is 4min; (2) Placing the pretreated body particles in a mold and performing hot pressing-quenching treatment: preheating the pretreated body particles to 175°C and pressurizing to 3MPa; then performing a first-stage pressurization at 6MPa and 195°C and keeping the temperature for 3min; then performing a second-stage pressurization at 15MPa and 203°C, using gradient temperature control: the temperature difference between the surface layer and the core layer is 18°C; then performing liquid nitrogen quenching, with a flow rate of 35L / min and a holding pressure of 11MPa; then cooling to below 80°C and demolding to obtain the pretreated body; (3) PVD coating is performed on the pre-treated body, and Al2O3 with a mass ratio of 7:3 is used for magnetron sputtering. 2 O 3 / TiO 2Composite target, substrate temperature: 100°C, sputtering power: 250W, film thickness: 80nm, and a conductive material based on TPU composite carbon nanotubes was obtained.

[0043] The pretreatment of homogeneous TPU comprises the following steps: ① Plasma activation: The homogeneous TPU is treated with atmospheric pressure dielectric barrier discharge equipment, with a power density of 3W / cm², a processing speed of 2m / min, a residence time of 120s, and a TPU surface temperature of 48°C; ② In-situ amination strengthening: 10wt% of ethylenediamine was dissolved in a mixed solvent of ethanol / water with a volume ratio of 7:3, and 0.4% of polyether-modified siloxane was added as a penetrant; then the product treated in step ① was added to the penetrant, and ultrasonically treated at 65°C for 2.8h. The endpoint was determined by the surface Zeta potential of +40mV, and the pretreated homogeneous TPU was obtained.

[0044] The treatment method for the composite of aminated MXene and chopped carbon fiber is as follows: Aminated MXene dispersion: add the aminated MXene powder into deionized water and perform ultrasonic treatment in an ice bath: 40kHz, 500W, 40min; then immerse the chopped carbon fiber in the aminated MXene dispersion, vacuum filter, and vacuum dry at 50°C for 5h to obtain an aminated MXene / chopped carbon fiber composite.

[0045] The hybridization treatment method of multi-walled carbon nanotubes and zirconium phosphate is as follows: multi-walled carbon nanotubes and zirconium phosphate are taken at a mass ratio of 1:0.3, and then subjected to hydrothermal treatment, reacted at 200°C for 10 hours at a filling degree of 75%, to obtain hybridized multi-walled carbon nanotubes-zirconium phosphate.

[0046] Conductive materials based on TPU composite carbon nanotubes are used in the field of anti-interference of vehicle-mounted electronic equipment.

[0047] Example 3 The conductive material based on TPU composite carbon nanotubes includes the following raw materials in parts by weight: homogeneous TPU: 78 parts; multi-walled carbon nanotubes: 8 parts; amino MXene: 3 parts; short-cut carbon fiber: 5 parts; doped polyaniline: 2 parts; zirconium phosphate nanosheets: 1 part; ionic liquid [VBIM] Br: 1.5 parts; hydrophobic nano-SiO 2 : 2 parts; silane coupling agent: 1 part; antioxidant: 0.5 parts; zinc stearate: 1 part. The length of the chopped carbon fiber is 5 mm, the silane coupling agent is KH550, and the antioxidant is 1076.

[0048] The preparation method of homogeneous TPU comprises the following steps: Ⅰ. Dehydrate PTMG with a molecular weight of 2000 under vacuum at 110°C for 3 hours; cool to 85°C, add MDI and dibutyltin dilaurate, and mechanically stir at 200 rpm for 3 hours under nitrogen protection; Ⅱ. The product obtained in step Ⅰ is cooled to 80℃, and the mixture of ethylenediamine / epoxy monomer and anti-hydrolysis agent are added, followed by shearing and emulsification at 5500rpm for 20min; poured into a polytetrafluoroethylene mold, and aged at 115℃ for 5h to obtain a homogeneous TPU. The mass fractions of each raw material are: PTMG: 100 parts; MDI: 35 parts; ethylenediamine: 8 parts; epoxy monomer: 3 parts; dibutyltin dilaurate: 0.05 parts; anti-hydrolysis agent: 1 part; the epoxy monomer is glycidyl methacrylate or glycidyl acrylate; the anti-hydrolysis agent is carbodiimide or polycarbodiimide.

[0049] The method for preparing the conductive material based on TPU composite carbon nanotubes comprises the following steps: (1) Each raw material was sequentially added into a twin-screw extruder for multi-stage melt blending and granulation: in the feeding section at 160°C, pretreated homogeneous TPU and zinc stearate were added, and the feeding rate was controlled at 8 kg / h; in the melting section, at 180°C, the composite amino MXene and chopped carbon fibers, hybridized multi-walled carbon nanotubes and zirconium phosphate were introduced as fillers, and preliminary dispersion was achieved by rotating the screw at a medium speed of 300 rpm; in the mixing section, at 195°C, doped polyaniline, ionic liquid [VBIM]Br and silane coupling agent were simultaneously injected, and the mixture was stirred for 1500 s. -1 The directional construction and interface bonding of the conductive network are achieved under the action of the high shear zone; in the homogenization stage, at 180 ° C, nano-SiO 2 and antioxidant, and remove volatile components under -0.08MPa vacuum conditions to obtain pre-treated particles, the whole melt pressure is 12MPa, and the total material residence time is 4.5min; (2) Placing the pretreated body particles in a mold and performing hot pressing-quenching treatment: preheating the pretreated body particles to 180°C and pressurizing to 4MPa; then performing a first-stage pressurization at 8MPa and 200°C and keeping the temperature for 3min; then performing a second-stage pressurization at 15MPa and 205°C, using gradient temperature control: the temperature difference between the surface layer and the core layer is 20°C; then performing liquid nitrogen quenching, with a flow rate of 50L / min and a holding pressure of 12MPa; then cooling to below 80°C and demolding to obtain the pretreated body; (3) PVD coating is performed on the pre-treated body, and Al2O3 with a mass ratio of 7:3 is used for magnetron sputtering. 2 O 3 / TiO 2 Composite target, substrate temperature: 120°C, sputtering power: 300W, film thickness: 100nm, and a conductive material based on TPU composite carbon nanotubes was obtained.

[0050] The pretreatment of homogeneous TPU comprises the following steps: ① Plasma activation: The homogeneous TPU is treated with atmospheric pressure dielectric barrier discharge equipment, with a power density of 3.2W / cm², a processing speed of 2m / min, a residence time of 120s, and a TPU surface temperature of 48°C; ② In-situ amination strengthening: 12wt% of ethylenediamine was dissolved in a mixed solvent of ethanol / water with a volume ratio of 7:3, and 0.5% of polyether-modified siloxane was added as a penetrant; then the product treated in step ① was added to the penetrant, and ultrasonically treated at 67°C for 3h. The endpoint was determined by the surface Zeta potential of +40mV to obtain the pretreated homogeneous TPU.

[0051] The treatment method for the composite of aminated MXene and chopped carbon fiber is as follows: Aminated MXene dispersion: add the aminated MXene powder into deionized water and perform ultrasonic treatment in an ice bath: 40kHz, 500W, 60min; then immerse the chopped carbon fiber in the aminated MXene dispersion, vacuum filter, and vacuum dry at 60°C for 6h to obtain an aminated MXene / chopped carbon fiber composite.

[0052] The hybridization treatment method of multi-walled carbon nanotubes and zirconium phosphate is as follows: multi-walled carbon nanotubes and zirconium phosphate are taken at a mass ratio of 1:0.5, and then subjected to hydrothermal treatment, reacting at 220°C for 12 hours at a filling degree of 80%, to obtain hybridized multi-walled carbon nanotubes-zirconium phosphate.

[0053] Conductive materials based on TPU composite carbon nanotubes are used in the field of electromagnetic protection of aircraft composite materials.

[0054] Comparative Example 1 Compared with Example 1, the difference is that the MXene is not aminated.

[0055] Comparative Example 2 Compared with Example 1, the difference is that PANI and ionic liquid are not added.

[0056] Comparative Example 3 Compared with Example 1, the difference is that the hot pressing-quenching treatment is not adopted.

[0057] Comparative Example 4 Compared with Example 1, the difference is that the surface of TPU is not modified.

[0058] The test data of the electromagnetic shielding performance of Examples 1-3 and Comparative Examples 1-4 are shown in Table 1.

[0059] The test data of the mechanical properties of Examples 1-3 and Comparative Examples 1-4 are shown in Table 2.

[0060] The test data of the environmental stability of Examples 1-3 and Comparative Examples 1-4 are shown in Table 3.

[0061] The test data of the electrical conductivity of Examples 1-3 and Comparative Examples 1-4 are shown in Table 4.

[0062] Table 1: Test data of electromagnetic shielding performance of Examples 1-3 and Comparative Examples 1-4

[0063] From the test data in Table 1, it can be seen that the absorption loss ratio of the amino-modified MXene (Example 2) is increased to 58% through the interface polarization effect, which is 23% higher than that of the untreated comparative example 1 (35%); the gradient hot pressing structure (Example 2) has a low-frequency (1GHz) reflection loss reduced to 42%, and a high-frequency (18GHz) absorption loss ratio of 65%, achieving broadband and efficient shielding; after removing PANI and ionic liquid (Comparative Example 2), the conductive network is discontinuous.

[0064] Table 2: Test data of mechanical properties of Examples 1-3 and Comparative Examples 1-4

[0065] From the test data in Table 2, it can be seen that in Example 2, CF forms a 3D skeleton, MXene sheets disperse stress, and the bending strength is increased to 50.1MPa (only 28.5MPa in Comparative Example 4); the impact strength of Example 2 reaches 56kJ / m², which is 47% higher than that of Comparative Example 2 (38kJ / m²), which is attributed to the energy dissipation mechanism of the hydrogen bond network; the tensile strength of Example 2 is 30.8MPa, which is 1.7 times that of Comparative Example 4, proving the effectiveness of amino interface bonding.

[0066] Table 3: Test data of environmental stability of Examples 1-3 and Comparative Examples 1-4

[0067] From the test data in Table 3, it can be seen that the water vapor permeability of Example 2 is only 1.2g / (m²·day), and the SE retention rate after wet heat aging is >95%; the contact angle of Example 2 is 152°, and there is no surface corrosion after the salt spray test; the performance of the unmodified TPU (Comparative Example 4) is significantly reduced due to interfacial hydrolysis.

[0068] Table 4: Test data of electrical conductivity of Examples 1-3 and Comparative Examples 1-4

[0069] From the test data in Table 4, it can be seen that in Example 2, multi-walled carbon nanotubes and amino-modified MXene form a "line-surface" conductive network with a volume resistivity as low as 6.8×10²Ω·cm. In Example 2, doped PANI and ionic liquid [VBIM]Br form a dynamic hydrogen bond network, and the surface resistivity drops to 5.2×10³Ω / sq. The surface CNTs concentration gradient (8%→5%) reduces the interface reflection impedance, improves the connectivity of the conductive network, and the resistance change rate after wet heat aging is only +6.8%. Comparative Example 4 (unmodified TPU): The filler is severely agglomerated, the conductive network is broken, and the resistivity exceeds 9.4×10 4 Ω / sq.

Claims

1. A conductive material based on TPU composite carbon nanotubes, characterized in that: The invention comprises the following raw materials in parts by weight: homogeneous TPU: 70-78 parts; multi-walled carbon nanotubes: 5-8 parts; amino MXene: 1-3 parts; short-cut carbon fibers: 2-5 parts; doped polyaniline: 0.5-2 parts; zirconium phosphate nanosheets: 0.3-1 parts; ionic liquid [VBIM] Br: 1-1.5 parts; hydrophobic nano-SiO2: 1-2 parts; Silane coupling agent: 0.5-1 part; Antioxidant: 0.3-0.5 parts; Zinc stearate: 0.5-1 part.

2. The conductive material based on TPU composite carbon nanotubes according to claim 1, characterized in that: The length of the chopped carbon fiber is 3-5 mm, the silane coupling agent is KH550, and the antioxidant is 1076.

3. The conductive material based on TPU composite carbon nanotubes according to claim 1, characterized in that: The preparation method of the homogeneous TPU comprises the following steps: Ⅰ. Dehydrate PTMG with a molecular weight of 2000 at 105-110°C in vacuum for 2-3 hours; cool to 85°C, add MDI and dibutyltin dilaurate, and mechanically stir at 200 rpm for 2.5-3 hours under nitrogen protection; Ⅱ. The product obtained in step Ⅰ is cooled to 75-80 ℃, and an ethylenediamine / epoxy monomer mixture and an anti-hydrolysis agent are added, followed by shear emulsification at 5000-5500 rpm for 10-20 min; poured into a polytetrafluoroethylene mold, and aged at 110-115 ℃ for 4-5 h to obtain a homogeneous TPU.

4. The conductive material based on TPU composite carbon nanotubes according to claim 3, characterized in that: The mass parts of each raw material are: PTMG: 100 parts; MDI: 32-35 parts; Ethylenediamine: 6-8 parts; epoxy monomer: 2-3 parts; dibutyltin dilaurate: 0.02-0.05 parts; anti-hydrolysis agent: 0.5-1 parts; the epoxy monomer is one of glycidyl methacrylate or glycidyl acrylate; the anti-hydrolysis agent is one of carbodiimide or polycarbodiimide.

5. A method for preparing a conductive material based on TPU composite carbon nanotubes according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Each raw material is added to a twin-screw extruder in turn for multi-stage melt blending and granulation: in the feeding section at 150-160°C, pretreated homogeneous TPU and zinc stearate are added, and the feeding rate is controlled at 5-8 kg / h; in the melting section, at 170-180°C, the composite amino MXene and chopped carbon fibers, hybridized multi-walled carbon nanotubes and zirconium phosphate are introduced as fillers, and preliminary dispersion is achieved by rotating the screw at a medium speed of 200-300 rpm; in the mixing section, at 185-195°C, doped polyaniline, ionic liquid [VBIM]Br and silane coupling agent are simultaneously injected at 1200-1500 s -1 The directional construction and interface bonding of the conductive network are achieved under the action of the high shear zone; in the homogenization stage, hydrophobic nano-SiO2 and antioxidants are added at 175-180°C, and the volatile components are removed under a vacuum condition of -0.06~-0.08MPa to obtain pre-treated particles. The whole melt pressure is 8-12MPa, and the total residence time of the material is 3.5-4.5min; (2) Placing the pretreated body particles in a mold and performing hot pressing-quenching treatment: preheating the pretreated body particles to 170-180°C and pressurizing to 2-4MPa; then performing a first-stage pressurization at 5-8MPa and 190-200°C, and keeping the temperature for 2-3min; then performing a second-stage pressurization at 10-15MPa and 200-205°C, using gradient temperature control: the temperature difference between the surface layer and the core layer is 15-20°C; then performing liquid nitrogen quenching, with a flow rate of 20-50L / min and a holding pressure of 10-12MPa; then cooling to below 80°C for demolding to obtain the pretreated body; (3) The pretreated body is subjected to PVD coating, and a composite target of Al2O3 / TiO2 with a mass ratio of 7:3 is selected for magnetron sputtering, substrate temperature: 80-120°C, sputtering power: 200-300W, film thickness: 50-100nm, to obtain a conductive material based on TPU composite carbon nanotubes.

6. The method for preparing a conductive material based on TPU composite carbon nanotubes according to claim 5, characterized in that: The pretreatment of the homogeneous TPU comprises the following steps: ① Plasma activation: The homogeneous TPU is treated with atmospheric pressure dielectric barrier discharge equipment, with a power density of 2.8-3.2W / cm², a processing speed of 2m / min, a residence time of 120s, and a TPU surface temperature of <50°C; ② In-situ amination strengthening: 8-12wt% of ethylenediamine is dissolved in a mixed solvent of ethanol / water with a volume ratio of 7:3, and 0.3-0.5% of polyether modified siloxane is added as a penetrant; then the product treated in step ① is added to the penetrant, and ultrasonically treated at 63-67°C for 2.5-3h. The endpoint is determined by the surface Zeta potential ≥+40mV, and the pretreated homogeneous TPU is obtained.

7. The method for preparing a conductive material based on TPU composite carbon nanotubes according to claim 5, characterized in that: The treatment method for the composite of the aminated MXene and chopped carbon fiber is as follows: aminated MXene dispersion: adding the aminated MXene powder into deionized water, and ultrasonically treating it in an ice bath: 40kHz, 500W, 20-60min; then immersing the chopped carbon fiber in the aminated MXene dispersion, vacuum filtering, and vacuum drying at 40-60°C for 4-6h to obtain an aminated MXene / chopped carbon fiber composite.

8. The method for preparing a conductive material based on TPU composite carbon nanotubes according to claim 5, characterized in that: The hybridization treatment method of multi-walled carbon nanotubes and zirconium phosphate is as follows: multi-walled carbon nanotubes and zirconium phosphate are taken at a mass ratio of 1: (0.2-0.5), and then subjected to hydrothermal treatment, reacting at a filling degree of 70-80% and 180-220° C. for 6-12 hours to obtain hybridized multi-walled carbon nanotubes-zirconium phosphate.

9. An application of a conductive material based on TPU composite carbon nanotubes according to any one of claims 1 to 4, characterized in that: Used in the field of anti-interference of vehicle-mounted electronic equipment or electromagnetic protection of aircraft composite materials.

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