Preparation method of long-chain Schiff base synergistic carbon nanotube fabric

Abstract

The invention discloses an electromagnetic shielding fabric spraying liquid and a preparation method and application thereof.The preparation method comprises the steps that p-benzoquinone and p-phenylenediamine serve as reactants, anhydrous zinc chloride serves as a catalyst, the reactants are fully stirred and dissolved in absolute ethyl alcohol, after an oil bath heating reaction is conducted, ethyl alcohol washing is conducted, vacuum drying is conducted in a vacuum drying oven, and long-chain Schiff base powder is obtained; the preparation method comprises the following steps: ultrasonically dispersing multi-walled carbon nanotube powder and N, N-dimethylformamide, dissolving Schiff base powder in a dispersion liquid of the multi-walled carbon nanotubes to prepare an electromagnetic shielding fabric spraying liquid, and spraying the obtained solution on a cotton fabric to obtain the cotton fabric loaded with long-chain Schiff base and the multi-walled carbon nanotubes. The prepared cotton fabric has excellent electromagnetic shielding performance, and the method has the advantages of being efficient, simple, economical and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of nano functional materials and textiles, and particularly relates to a method for preparing a long-chain Schiff base coordinated carbon nanotube fabric. Background Art

[0002] The discovery and widespread application of electromagnetic waves have improved people's lives and promoted social development. However, every coin has its downsides. During their propagation, electromagnetic waves generate disordered electromagnetic radiation, which not only affects the normal operation of equipment but can even threaten human health. Effectively reducing or even eliminating the harmful effects of electromagnetic waves on equipment and the human body can be addressed in two ways: first, source improvement: optimizing the electronic circuit design of the equipment; and second, external protection: developing external electromagnetic shielding or absorption materials. Compared to source improvement, external protection has a wider range of applications, is easier to design, and simpler to operate. Therefore, the need to develop high-performance electromagnetic shielding or absorption materials is increasingly urgent. Cotton fabrics inherently have weak electromagnetic wave shielding capabilities. Cotton fibers have weak electrical conductivity, insufficient to directly shield electromagnetic waves. However, through special treatments or the addition of conductive materials, the electromagnetic shielding properties of cotton fabrics can be enhanced. Organic Schiff base compounds also feature light weight and low density, and, in particular, a minimal temperature rise when converting electromagnetic waves into energy. These characteristics of Schiff base materials undoubtedly make them a shining light in the field of electromagnetic absorption materials.

[0003] Since fabric modification research involves multiple disciplines such as textiles, materials, photochemistry, and the environment, it is quite difficult. Although a lot of research has been done on the electromagnetic wave shielding of Schiff bases at home and abroad, and great progress has been made, there is still some distance to go before it can be applied to fabrics. Therefore, if it is to be truly applied in real life, it is necessary to continue to conduct extensive research on improving the application of Schiff bases. Summary of the Invention

[0004] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a long-chain Schiff base-synergistic carbon nanotube fabric.

[0007] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing a long-chain Schiff base-coordinated carbon nanotube fabric, characterized in that: it comprises:

[0008] The p-phenylenediamine, anhydrous ethanol and zinc chloride are mixed and stirred, and a p-benzoquinone ethanol solution is added, condensed and refluxed, centrifuged, and the precipitate is collected, dried and ground to prepare a p-benzoquinone p-phenylenediamine long-chain Schiff base;

[0009] The multi-walled carbon nanotubes are dispersed in N,N-dimethylformamide, ultrasonicated, and p-benzoquinone p-phenylenediamine long-chain Schiff base is added and magnetically stirred to prepare a spraying liquid;

[0010] The spraying liquid is evenly sprayed on the surface of the fabric, dried, and the spraying-drying steps are repeated 50 to 150 times to prepare a long-chain Schiff base coordinated carbon nanotube fabric.

[0011] As a preferred embodiment of the preparation method of the present invention, the usage ratio of p-phenylenediamine, anhydrous ethanol and zinc chloride is 0.01-0.02 mol: 20-40 ml: 0.15-0.3 g.

[0012] As a preferred embodiment of the preparation method of the present invention, the molar ratio of p-benzoquinone to ethanol in the p-benzoquinone ethanol solution is 0.01-0.02 mol:20-40 ml, and the molar ratio of p-benzoquinone to p-phenylenediamine is 1:1.

[0013] As a preferred embodiment of the preparation method of the present invention, the multi-walled carbon nanotubes are dispersed in N,N-dimethylformamide, wherein the ratio of the multi-walled carbon nanotubes to N,N-dimethylformamide is 0.5-2 g:100 mol.

[0014] As a preferred embodiment of the preparation method of the present invention, the mass ratio of the multi-walled carbon nanotubes to the p-benzoquinone-p-phenylenediamine long-chain Schiff base is 1:2-8.

[0015] As a preferred embodiment of the preparation method of the present invention, the temperature of the ultrasonic treatment is 30-40°C.

[0016] As a preferred embodiment of the preparation method of the present invention, the magnetic stirring rate is 800 r / min.

[0017] As a preferred embodiment of the preparation method of the present invention, the spraying liquid is evenly sprayed on the surface of the fabric, wherein the spraying thickness is controlled to be 0.5 to 2 mm.

[0018] Another object of the present invention is to overcome the deficiencies in the prior art and provide a long-chain Schiff base synergistic carbon nanotube fabric.

[0019] Another object of the present invention is to overcome the deficiencies in the prior art and provide an application of a long-chain Schiff base in conjunction with a carbon nanotube fabric in an electromagnetic shielding fabric.

[0020] Beneficial effects of the present invention:

[0021] (1) This invention significantly improves electromagnetic shielding effectiveness, is easy to operate, low-cost, and environmentally friendly, and has great potential, especially in the high-tech field. Its excellent durability and stability ensure long-term use and provide new ideas and methods for the research and development of electromagnetic shielding materials. This innovative method not only improves electromagnetic shielding effectiveness, but also promotes the research and development of environmentally friendly materials, demonstrating the perfect combination of technology and environmental protection.

[0022] (2) This invention achieves higher shielding effectiveness while reducing material costs and enhancing market competitiveness by further optimizing the spraying process and material ratio. In subsequent research, the team will continue to explore the optimal dosage of Schiff base and carbon nanotubes in different ratios to further enhance shielding effectiveness. At the same time, they plan to introduce nanocomposites to enhance the mechanical strength and weather resistance of the coating, ensuring its stable performance in extreme environments.

[0023] (3) The present invention improves production efficiency, reduces manual errors, and ensures consistency in product quality by optimizing the intelligent control of spraying equipment. Through multidisciplinary integration, we strive to achieve more breakthroughs in the field of electromagnetic shielding and contribute to scientific and technological progress. We further optimize the spraying process and improve the level of material intelligence. Through big data analysis and cloud computing, we accurately control the spraying parameters to ensure the uniformity and stability of the coating, strive to achieve more innovative breakthroughs in the field of electromagnetic shielding, and promote the deep integration of scientific and technological progress and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0025] Figure 1 The electromagnetic shielding effectiveness of long-chain Schiff base synergistically with carbon nanotube fabrics.

[0026] Figure 2 The electromagnetic shielding effectiveness of polyethylene glycol carbon nanotube fabric.

[0027] Figure 3 The electromagnetic shielding effectiveness of cotton fabric.

[0028] Figure 4These are the XRD patterns of cotton fabric, Schiff base carbon nanotube fabric and polyethylene glycol carbon nanotube fabric.

[0029] Figure 5 SEM images of Schiff base: carbon nanotube (4:1) cotton fabric at different magnifications.

[0030] Figure 6 SEM images of Schiff base: carbon nanotube (6:1) cotton fabric at different magnifications.

[0031] Figure 7 SEM images of Schiff base: carbon nanotube (8:1) cotton fabric at different magnifications.

[0032] Figure 8 These are SEM images of polyethylene glycol: carbon nanotube (6:1) cotton fabric at different magnifications.

[0033] Figure 9 These are SEM images of polyethylene glycol: carbon nanotube (8:1) cotton fabric at different magnifications.

[0034] Figure 10 This is the SEM image of cotton fabric.

[0035] Figure 11 SEM comparison of cotton fabric and Schiff base fabric.

[0036] Figure 12 This is the SEM comparison picture of cotton fabric and polyethylene glycol fabric. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0038] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0039] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0040] The raw materials used in the present invention are: p-phenylenediamine, anhydrous zinc chloride, N,N-dimethylformamide (Shanghai McLean Biochemical Technology Co., Ltd.), polyethylene glycol 2000 (Sinopharm Chemical Reagent Co., Ltd.), anhydrous ethanol (Shanghai Titan Technology Co., Ltd.), multi-walled carbon nanotubes (Suzhou Carbon Graphene Technology Co., Ltd.), p-benzoquinone (Chengdu Aike Chemical Reagent Co., Ltd.), and deionized water.

[0041] Instruments used in the examples of the present invention: F-101S heat-collecting constant temperature heating magnetic stirrer (Zhengzhou Ketai Experimental Equipment Co., Ltd.), JB-3 timed bidirectional magnetic constant temperature stirrer (Jintan Jinfen Instrument Co., Ltd.), LC-JY92-IIDN ultrasonic cell disruptor (Shanghai Lichen Instrument Technology Co., Ltd.), H1750 high-speed desktop centrifuge (Hunan Xiangyi Laboratory Instrument Development Co., Ltd.), Nova Nano SEM 450 field emission scanning electron microscope (FEI Company, USA), NEXUS-670 Fourier transform infrared spectrometer (Nicolet Company, USA), D / max2500PC X-ray diffractometer (Shimadzu Corporation, Japan), ESCALAB 250Xi X-ray photoelectron spectrometer (Thermo Fisher Scientific Inc.), RTS-8 four-point probe instrument (Guangzhou Four Probe Technology Co., Ltd.), DR-913G fabric electromagnetic radiation protection performance tester (Wenzhou Dayong Textile Instrument Co., Ltd.), high-temperature gel permeation chromatography coupled with 18-angle laser light scattering system (DAWN HELEOSⅡ, Agilent, USA & PL-GPC 220, Wyatt, USA).

[0042] The performance testing methods in the embodiments of the present invention are: the conductive performance adopts the four-probe method, and the electromagnetic shielding effectiveness adopts the coaxial flange method.

[0043] Example 1

[0044] This embodiment provides a method for preparing a long-chain Schiff base-coordinated carbon nanotube fabric, comprising the following steps:

[0045] (1) Preparation of p-benzoquinone p-phenylenediamine long-chain Schiff base:

[0046] Add 0.02 mol of p-phenylenediamine, 40 mL of anhydrous ethanol and 0.3 g of ZnCl2 to a round-bottom flask and stir until completely dissolved. Then weigh 0.02 mol of p-benzoquinone and mix evenly with 40 mL of anhydrous ethanol. Then slowly add it dropwise to the round-bottom flask at a rate of 2 d / s. Condensate and reflux at 70 ° C in an oil bath and stir to react for 8 hours. After the reaction is completed, take out the solution and centrifuge it with anhydrous ethanol at 10000 r / min for several times, each time for 5 minutes, until the solution and precipitate are separated. Dry the precipitate in a vacuum at 60 ° C for 12 hours, take it out and grind it to obtain a brown powder product, which is the p-benzoquinone p-phenylenediamine long-chain Schiff base.

[0047] The molecular weight of the obtained p-benzoquinone p-phenylenediamine long-chain Schiff base was determined: a small amount of sample was dissolved in HPLC-grade tetrahydrofuran as the solvent, and the insoluble matter was removed. The molecular weight of the sample was determined by GPC gel permeation chromatography. The number average molecular weight Mn of the obtained poly Schiff base was 1018, the weight average molecular weight Mw was 1099, and the dispersion index PDI was 1.08.

[0048] (2) Preparation of long-chain Schiff base-coordinated multi-walled carbon nanotubes:

[0049] Take a Schiff base and multi-walled carbon nanotube powder in a mass ratio of 2:1, disperse the multi-walled carbon nanotubes in 50 ml of N,N-dimethylformamide, wherein the amount ratio of multi-walled carbon nanotubes to N,N-dimethylformamide is 1g:100mol, then ultrasonically treat at a power of 50% and a temperature of 40°C for 1 hour, add the prepared long-chain Schiff base powder, and continue magnetic stirring at 800r / min for 30 minutes to ensure uniform dispersion to obtain a spray liquid.

[0050] (3) Finishing fabrics:

[0051] In a fume hood, the prepared spray solution was evenly sprayed onto the fabric surface, controlling the coating thickness to 0.651 mm to ensure uniform coverage. The fabric was then dried in a 60°C oven, repeating this process 50 times on the front and 50 times on the back to fully cure the fabric. This resulted in a long-chain Schiff base-synergized carbon nanotube fabric.

[0052] Example 2

[0053] The difference between this embodiment and embodiment 1 is that the ratio of Schiff base to multi-walled carbon nanotube powder in step (2) is replaced with 4:1, the thickness of the spraying in step (3) is controlled to be 0.763 mm, and the remaining steps are the same as in embodiment 1 to obtain a long-chain Schiff base-synergistic carbon nanotube fabric.

[0054] Example 3

[0055] The difference between this embodiment and embodiment 1 is that the ratio of Schiff base to multi-walled carbon nanotube powder in step (2) is replaced with 6:1, the thickness of the spraying in step (3) is controlled to be 1.229 mm, and the remaining steps are the same as in embodiment 1 to obtain a long-chain Schiff base synergistic carbon nanotube fabric.

[0056] Example 4

[0057] The difference between this embodiment and embodiment 1 is that the ratio of Schiff base to multi-walled carbon nanotube powder in step (2) is replaced with 8:1, the thickness of the spraying in step (3) is controlled to be 1.575 mm, and the remaining steps are the same as in embodiment 1 to obtain a long-chain Schiff base-synergistic carbon nanotube fabric.

[0058] The electromagnetic shielding effectiveness of the long-chain Schiff base synergistic carbon nanotube fabrics prepared in Examples 1 to 4 is as follows: Figure 1 As shown, among them, (a) Schiff base: carbon nanotube (8:1) cotton fabric; (b) Schiff base: carbon nanotube (6:1) cotton fabric; (c) Schiff base: carbon nanotube (2:1) cotton fabric; (d) Schiff base: carbon nanotube (4:1) cotton fabric.

[0059] It can be seen that a 4:1 ratio of Schiff base to carbon nanotubes achieves optimal electromagnetic shielding effectiveness, exceeding 15dB in the 0-3GHz frequency band and reaching a maximum of 20dB. This surpasses the electromagnetic shielding effectiveness of carbon nanotubes and raw cotton, and shows an upward trend. At a 4:1 ratio (20% carbon nanotubes), the carbon nanotube content is moderate and evenly dispersed, forming a continuous conductive path. Electromagnetic waves are effectively shielded by surface reflection losses. The combination of the conductive network and the dielectric matrix results in good dispersion, with fewer internal pores and defects in the material. Electromagnetic waves are gradually dissipated within the confined space through multiple reflections. At a 2:1 ratio (33.3% carbon nanotubes), the slightly higher carbon nanotube content is prone to agglomeration, resulting in excessive local conductivity and uneven overall dispersion. "Islands" form in some areas, reducing the effective reflection area. CNT agglomeration creates localized areas of high conductivity, leading to impedance mismatch at mid- and high-frequency frequencies. 6:1 and 8:1 (14.3% and 11.1% carbon nanotubes), the carbon nanotube content is insufficient to form a continuous network, and the electromagnetic waves are not fully reflected after penetrating the material. The Schiff base ratio is high, but the insufficient carbon nanotubes lead to low conductivity, limited absorption loss capacity, limited multiple reflection paths, and delayed dielectric response at high frequencies.

[0060] Comparative Example 1

[0061] This embodiment provides a method for preparing polyethylene glycol carbon nanotube fabric, comprising the following steps:

[0062] (1) Preparation of polyethylene glycol-multi-walled carbon nanotube spraying liquid:

[0063] Take polyethylene glycol and multi-walled carbon nanotube powder in a mass ratio of 2:1, disperse the multi-walled carbon nanotubes in 50 ml of N,N-dimethylformamide, wherein the amount ratio of multi-walled carbon nanotubes to N,N-dimethylformamide is 1g:100mol, then ultrasonically treat at a power of 50% and a temperature of 40°C for 1 hour, add polyethylene glycol, and continue ultrasonic treatment for 30 minutes to ensure uniform dispersion to prepare a spray liquid.

[0064] (2) Finishing fabrics:

[0065] In a fume hood, the prepared spray solution was evenly sprayed onto the fabric surface, controlling the coating thickness to 0.524 mm to ensure uniform coverage. The fabric was then dried in a 60°C oven, repeating this process of spraying and drying until fully cured, producing a polyethylene glycol carbon nanotube fabric.

[0066] Comparative Example 2

[0067] The difference between this embodiment and comparative example 1 is that the ratio of polyethylene glycol to multi-walled carbon nanotube powder in step (1) is replaced with 4:1, the thickness of the spraying in step (2) is controlled to be 0.587 mm, and the remaining steps are the same as in embodiment 1 to obtain polyethylene glycol carbon nanotube fabric.

[0068] Comparative Example 3

[0069] The difference between this embodiment and comparative example 1 is that the ratio of polyethylene glycol to multi-walled carbon nanotube powder in step (1) is replaced with 6:1, the thickness of the spraying in step (2) is controlled to be 0.616 mm, and the remaining steps are the same as in embodiment 1 to obtain polyethylene glycol carbon nanotube fabric.

[0070] Comparative Example 4

[0071] The difference between this embodiment and comparative example 1 is that the ratio of polyethylene glycol to multi-walled carbon nanotube powder in step (1) is replaced with 8:1, the thickness of the spraying in step (2) is controlled to be 0.750 mm, and the remaining steps are the same as in embodiment 1 to obtain polyethylene glycol carbon nanotube fabric.

[0072] The electromagnetic shielding effectiveness of the polyethylene glycol carbon nanotube fabrics prepared in Examples 1 to 4 is as follows: Figure 2 As shown, among them, (a) polyethylene glycol: carbon nanotube (2:1) cotton fabric; (b) polyethylene glycol: carbon nanotube (4:1) cotton fabric; (c) polyethylene glycol: carbon nanotube (6:1) cotton fabric; (d) polyethylene glycol: carbon nanotube (8:1) cotton fabric.

[0073] It can be seen that an 8:1 ratio of polyethylene glycol (PEG) to carbon nanotubes achieves optimal electromagnetic shielding effectiveness, reaching a maximum of 16.5 dB in the 0-3 GHz frequency band. At an 8:1 ratio, the PEG concentration is extremely high as a dispersant. Through molecular chain entanglement and hydrogen bonding, a small number of carbon nanotubes are dispersed ultra-evenly on the cotton fabric surface, preventing aggregation. The evenly dispersed carbon nanotubes cover the pores of the cotton fibers, forming a dense but discontinuous conductive coating, reducing direct electromagnetic wave penetration paths. At a 6:1 ratio, PEG still dominates, but the carbon nanotube concentration increases slightly, leading to the formation of tiny conductive clusters in some areas, creating a localized conductive network. Polarization synergy exists at the interface between the conductive clusters and the PEG matrix. These tiny clusters act as nanoantennas at high frequencies, absorbing electromagnetic waves through localized surface plasmon resonance (LSPR). While electromagnetic shielding effectiveness is significantly improved in the resonant frequency band, it declines in the non-resonant frequency band, resulting in overall performance weaker than that of the 8:1 ratio. At a 4:1 ratio, the PEG ratio decreases, the carbon nanotube dispersion decreases, and aggregates begin to form, leading to partial disruption of the conductive network. Agglomerates coexist with dispersed carbon nanotubes, forming a "conductive-insulating" hybrid structure with limited reflection and absorption efficiency. The conductive network is discontinuous, and the skin effect causes electromagnetic waves to concentrate in surface defect areas, enhancing transmission and further reducing electromagnetic shielding effectiveness. At a ratio of 2:1, the PEG content is extremely low and cannot effectively disperse the carbon nanotubes. The carbon nanotubes aggregate on the surface of the cotton fibers, and PEG is insufficient to wrap the carbon nanotube aggregates. The heterogeneous interface almost disappears, and the dielectric loss mechanism fails. Electromagnetic waves directly penetrate the insulating area, relying only on the intrinsic extremely low loss of cotton fabrics, and the electromagnetic shielding effectiveness is reduced to a minimum.

[0074] Comparative Example 5

[0075] This embodiment provides a common commercially available cotton fabric, which is the adjacent cotton fabric of the National Standard of the People's Republic of China GB / T7568.2-2008. Figure 3 This is the electromagnetic shielding effectiveness of the cotton fabric. It can be seen that natural cotton fibers have poor conductivity and limited shielding effectiveness, which is almost 0.

[0076] Example 5

[0077] This example is to analyze the conductivity of different fabrics prepared in the examples and comparative examples, specifically:

[0078] The sample was cut into a circle with a diameter of 10 cm. The conductivity was tested using the four-probe method with an RTS-8 four-point probe instrument (Guangzhou Four Probe Technology Co., Ltd.). The middle point and four surrounding points were tested and the average value was obtained. The results are shown in Table 1.

[0079] Table 1

[0080]

[0081] As can be seen, Schiff bases, which contain conjugated structures such as C=N and benzene rings, form strong interfacial coupling with carbon nanotubes at a 4:1 ratio ("uniformly distributed river"), significantly reducing interfacial resistance. Schiff bases disperse carbon nanotubes more evenly through π-π stacking, forming a highly interconnected conductive network. Chemical bonding enhances electron mobility, significantly increasing overall conductivity even at low carbon nanotube content. At a 2:1 ratio ("oasis in the desert"), the carbon nanotube content of 33.3% is well above the percolation threshold (15-20%). Localized aggregation blocks long-range conductive pathways, resulting in weak interfacial bonding between the Schiff base and the carbon nanotubes and low electron transfer efficiency. At 6:1 and 8:1 ratios, the carbon nanotube content falls below the percolation threshold, exposing the insulating properties of the overly thin cotton fabric and discontinuous conductive networks. Electrons are transported via quantum tunneling, and conductivity decreases exponentially with distance.

[0082] At a 4:1 ratio of polyethylene glycol (PEG): carbon nanotube (MWCNT), the hydrophilic (-OH) chains of PEG form hydrogen bonds with the hydroxyl groups on the cotton fiber surface, evenly anchoring the carbon nanotubes to the fiber surface and reducing the contact resistance caused by carbon nanotube slip. At a moderate carbon nanotube content, the dispersion capacity of the PEG matrix is ​​balanced with the carbon nanotube concentration, forming a uniform and continuous conductive network. The carbon nanotubes and PEG chains are in close contact through van der Waals forces or hydrogen bonds, improving electron tunneling efficiency. The porous structure of the cotton fiber attracts the carbon nanotubes through capillary action, enhancing their interfacial contact with PEG. At a 2:1 ratio, the excess carbon nanotubes aggregate in PEG due to hydrophobicity, disrupting the long-range conductive network. The polar chains of PEG are poorly compatible with the hydrophobic surface of the carbon nanotubes, exacerbating phase separation at high concentrations and reducing conductivity. At ratios of 6:1 and 8:1, carbon nanotube agglomeration decreased, but the spacing between carbon nanotubes was too large, electron transport relied on quantum tunneling, and the conductivity decreased (0.16 S / cm for 6:1). The unexpected rebound at 8:1 (0.2 S / cm) was due to the steric hindrance effect of the PEG molecular chain and the formation of clusters of carbon nanotubes at the intersection of fibers, which achieved short-range conduction through contact between fibers, resulting in a slight rebound in conductivity.

[0083] Example 6

[0084] This example is to perform X-ray diffraction analysis on different fabrics prepared in the examples and comparative examples, specifically:

[0085] A 1*1cm sample was tested using a D / max2500PC X-ray diffractometer (Shimadzu, Japan). The results are as follows: Figure 4 As shown, among them, (a) Schiff base: carbon nanotube (2:1) fabric (b) Schiff base: carbon nanotube (6:1) fabric (c) Schiff base: carbon nanotube (4:1) fabric (d) polyethylene glycol: carbon nanotube (4:1) fabric (e) polyethylene glycol: carbon nanotube (8:1) fabric (f) cotton fabric.

[0086] The peaks at 14.9°, 16.4°, and 22.65° for cotton fabric correspond to the (101), (10ī), and (002) crystal planes, respectively. The peaks are sharp and symmetrical, indicating high crystallinity and orderly fiber arrangement. The peak intensity at 23.28° for polyethylene glycol: carbon nanotubes (8:1) increases, and the peak of PEG's (032) crystal plane partially overlaps with the peak of cotton fabric's (002) crystal plane, forming a broadened peak. A new peak appears at 19.08°, corresponding to the (120) crystal plane of PEG, which corresponds to the crystalline structure of the PEG helical chain. The absence of a significant peak near 26° indicates that the carbon nanotubes are well dispersed or wrapped by PEG, without forming a clear graphite stacking structure. The intensities at 19.08° and 22.82° for polyethylene glycol: carbon nanotubes (4:1) are lower than those for 8:1, because the increased proportion of carbon nanotubes interferes with PEG crystallization. Schiff base: Carbon nanotubes (4:1) exhibit a peak at 5.88°. This is due to the layered stacking of Schiff base molecules, with carbon nanotubes intercalated between them. The intercalation of the carbon nanotubes and the conjugated structure of the Schiff base synergistically form an ordered composite phase. A strong peak at 22.68° corresponds to the interlayer spacing of the Schiff base (π-π stacking or intermolecular hydrogen bonding), while a weak peak at 26.16° indicates that the carbon nanotubes are well dispersed and the Schiff base is dominant. Schiff base: Carbon nanotubes (6:1) exhibit a peak at 5.92°, but it is weaker than that of the 4:1 sample. This is due to the reduced proportion of carbon nanotubes and insufficient support, which reduces the long-range order of the Schiff base layered stacking, resulting in smaller grain size or increased defect density, weakening the diffraction signal. The peak at 22.66° is higher than that of the 4:1 sample, indicating improved crystallinity. The peak at 26.2° is slightly higher than that of the 4:1 sample because the increased Schiff base ratio reduces the dispersion of the carbon nanotubes, exposing more graphitized regions. The Schiff base:carbon nanotube (2:1) mixture exhibits a weak peak at 26.16° due to the increased carbon nanotube content. The peak at 22.64° is slightly stronger than that of the 4:1 and 6:1 mixtures because the Schiff base reduces the complete coverage of the cotton fiber, partially exposing the cellulose peak at 22.7°. This peak then overlaps with the Schiff base peak at 22.64°, enhancing the apparent peak intensity.

[0087] Example 7

[0088] This example is a scanning electron microscope analysis of different fabrics prepared in the examples and comparative examples, specifically:

[0089] A 1*1 cm sample was taken and tested using a Nova Nano SEM 450 field emission scanning electron microscope (FEI, USA). Figure 5The following are SEM images of Schiff base: carbon nanotube (4:1) cotton fabric at different magnifications. At 500x magnification, the image shows a relatively uniform distribution of pores. The composite coating completely covers the cotton fiber surface without local accumulation or shedding. The natural grooves and pore structure of the cotton fiber are filled with the composite but still retain their morphology. There are no cracks or gaps at the interface between the coating and the fiber, indicating that the Schiff base is bound to the fiber molecules through hydrogen bonds or van der Waals forces, forming a stable multi-level interface. The irregular pores that appear increase the surface roughness of the material and significantly increase the specific surface area. At 1000x magnification, the irregular particles attached to the surface are Schiff base-carbon nanotube composites. The particles are evenly distributed on the fiber surface, proving that the modification process successfully introduced carbon nanotubes into the cotton fiber matrix, rather than just physical mixing. The fragmented structure indicates that the material is flexible and can withstand a certain degree of deformation without complete peeling. Under 2000x magnification, the coating surface shows a nano-scale rough texture, which is composed of Schiff base layered crystals and carbon nanotube ends. The carbon nanotubes are embedded in the Schiff base interlayer in the form of single roots or small bundles. Under 5000x magnification, a layered or mesh structure (carbon nanotube network) can be seen covering the fiber surface, forming a continuous conductive path. The carbon nanotubes have uniform diameters, a clean surface without impurities, and the axial arrangement direction is consistent with that of the Schiff base crystallites, indicating the presence of directed self-assembly behavior during the composite process. The nanoparticles of the Schiff base tightly wrap the surface of the carbon nanotubes, reducing the edge defects of the carbon nanotubes through chemical bonding. The interface between the carbon nanotubes and the Schiff base in the coating is seamlessly connected, with no visible gaps or phase separation, indicating that the two are extremely compatible.

[0090] Figure 6 SEM images of a Schiff base:carbon nanotube (CNT) (6:1) cotton fabric at different magnifications. At 800x magnification, a continuous, film-like or granular coating appears, with complete coating coverage. However, localized accumulation occurs, likely due to solution flow during spraying. The sparse, fibrous structure of the CNTs is embedded within the Schiff base film, forming localized "CNT-Schiff base" complex clusters. At 1000x magnification, approximately 70% of the CNTs are dispersed as single strands, while 30% are in small bundles. Schiff base nanoparticles are attached to the CNT surfaces. At 2000x magnification, the CNTs exhibit a smooth surface and uniform diameter, with no obvious signs of breakage or oxidation, indicating that the spraying process did not damage the CNT structure. At 5000x magnification, numerous Schiff base nanoparticles are attached to the CNT surfaces, with some CNTs completely encapsulated by the Schiff base, forming a "CNT@Schiff base" core-shell structure, bonded by π-π stacking or van der Waals forces. A small number of carbon nanotubes have etching marks on their surfaces (diameter mutations or surface pits), which may be caused by ultrasonic dispersion before spraying.

[0091] Figure 7The following are SEM images of a Schiff base:carbon nanotube (8:1) cotton fabric at different magnifications. At 250x magnification, the natural longitudinal grooves of the cotton fibers are clearly visible, and the surface is covered by a continuous coating, leaving the original fibers uncovered. The Schiff base-carbon nanotube composite exhibits granular accumulation, with the coating tightly adhering to the fiber grooves and exhibiting no delamination or cracking. This indicates that the Schiff base forms hydrogen bonds with the cellulose hydroxyl groups of the cotton fibers via polar groups (such as -OH and -NH). At 1000x magnification, the Schiff base matrix appears as a thin film covering the surface of the carbon nanotube network. Most of the carbon nanotubes are dispersed as single or bundles of 2-3. The carbon nanotubes are partially embedded in the Schiff base film, with the exposed segments physically anchored to the matrix. At 2000x magnification, the Schiff base forms a discontinuous coating on the carbon nanotube surface, enhancing interfacial bonding through π-π interactions or chemical bonding. At 5000x magnification, Schiff base nanoparticles are attached to the surface of a single carbon nanotube, and spiral textures can be seen on the carbon nanotube wall, indicating possible structural defects (such as dislocations). High-resolution Schiff base images reveal irregularly distributed nanopores, and the jagged edges of the cracks indicate a brittle fracture mode that requires toughening.

[0092] Figure 8 SEM images of a polyethylene glycol (PEG)-carbon nanotube (CNT) (6:1) cotton fabric at different magnifications are shown. At low magnification (250x), the coating shows uniform coverage on the cotton fiber surface. The composite forms a continuous film, completely enveloping the fiber substrate with no localized accumulation or loss. The natural grooves and microfibril structure of the cotton fiber are clearly visible, indicating that the coating does not disrupt the substrate morphology, but only forms a functional surface modification layer. No coating shedding, cracking, or CNT agglomeration was observed within the centimeter-scale field of view. At 2000x, the composite forms a dense three-dimensional network on the cotton fiber surface, with the CNTs embedded in the PEG matrix in a fibrous or bundled form, forming a multi-level conductive pathway. Uniformly distributed honeycomb pores are visible on the coating surface, with a regular pore structure likely formed by solvent evaporation or PEG crystallization. At 5000x, individual CNTs or small bundles of CNTs are clearly visible, forming a "bridging" structure with the PEG matrix. Some CNTs bridge adjacent fibers to form a continuous conductive pathway. The surface of the PEG matrix is ​​smooth, and there is no gap or peeling phenomenon at the interface between carbon nanotubes and PEG, indicating that the two are extremely compatible.

[0093] Figure 9The following are SEM images of polyethylene glycol: carbon nanotube (8:1) cotton fabric at different magnifications. At 500x magnification, the composite perfectly covers the cotton fiber surface in the form of a continuous film, and the original fiber weave structure is clearly visible, indicating a highly uniform spraying process with no large-scale shedding or faulting. The coating is tightly bonded to the fiber interface, and the micropores at the fiber intersections are naturally retained. At 2000x magnification, the coating exhibits a uniform submicron-scale porous structure, significantly increasing the specific surface area. The carbon nanotubes are directionally exposed from the PEG matrix, forming a local conductive network along the fiber surface. At 5000x magnification, the carbon nanotubes are uniformly embedded in the PEG matrix in the form of single strands or small bundles, with only localized controlled agglomeration, demonstrating that the 8:1 ratio successfully balances the synergistic effect of coating and exposure. Nanoscale cracks in the PEG film form an adaptive buffer zone to avoid large-scale brittle fracture.

[0094] Figure 10 This is an SEM image of cotton fabric. The typical morphology of cotton fibers is a flat, ribbon-like structure with a naturally twisted surface. The image shows a spiral or wavy arrangement of fibers along the axial direction. The cotton fiber surface displays longitudinal stripes or grooves, and the interlaced network structure of the fibers is clearly visible in the image. The layered structure of the cellulose fibrils is clearly visible, with relatively soft fiber edges.

[0095] Example 8

[0096] This example is to perform Fourier transform infrared spectroscopy analysis on different fabrics prepared in the examples and comparative examples, specifically:

[0097] A 1*1cm sample was tested using a NEXUS-670 Fourier transform infrared spectrometer (Nicolet, USA). Figure 11 These are SEM comparison images of cotton fabric and Schiff base fabric, including (a) infrared spectrum of cotton fabric (b) infrared spectrum of Schiff base: carbon nanotube (6:1) fabric (c) infrared spectrum of Schiff base: carbon nanotube (4:1) fabric (d) infrared spectrum of Schiff base: carbon nanotube (2:1) fabric.

[0098] 3214cm -1 The OH stretching vibration of cellulose in cotton fabric is at 1633cm -1 The stretching vibration of C=N (imine bond) of Schiff base is generated by the condensation of p-benzoquinone (C=O) and p-phenylenediamine (-NH2) to form imine (C=N). The characteristic stretching vibration peak of its C=N bond is at 1600-1680cm -1 Within the range of 1633cm -1 Completely consistent. No 1700cm -1 The C=O peak near 1558cm indicates that the reaction is complete. -1 The C=C stretching vibration of the aromatic ring is at 1484 cm-1 The C=C secondary vibration of the aromatic ring is 1427cm -1 The CH2 bending vibration of cotton cellulose is at 1171cm -1 The COC stretching vibration of cotton fabric cellulose is at 892cm -1 and 864cm -1 The out-of-plane bending vibration of the CH of the para-substituted benzene ring is 727 cm -1 The graphitized structure vibration of carbon nanotubes is shown in sp 2 Hybridized C=C skeleton.

[0099] Figure 12 SEM comparison of cotton fabric and polyethylene glycol fabric, including (a) infrared spectrum of cotton fabric and (b) infrared spectrum of polyethylene glycol: carbon nanotube (8:1) fabric.

[0100] In (a), at 3340 cm -1 The stretching vibration of hydroxyl (-OH) in cotton cellulose is at 2900 cm -1 The C—H stretching vibration is at 1430 cm -1 At 1370cm -1 The CH bending vibration is at 1160 cm -1 The COC asymmetric stretching vibration is at 1105cm -1 The CO stretching vibration of the ring is related to the skeleton vibration of the glucose ring. -1 The stretching vibration of CO further reflects the vibration mode of hydroxyl and ether bonds in cellulose. -1 The stretching vibration of CH is the symmetrical stretching vibration of the methylene group (-CH2-) in PEG. -1 At 1237 cm -1 The C-0-C asymmetric stretching vibration of PEG is at 1144 cm -1 The stretching vibration of the COC glycosidic bond in the cellulose of cotton fabric is 1087cm -1 The C-0-C symmetric stretching vibration of PEG is shown in Fig.

[0101] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A method for preparing a long-chain Schiff base-synergistic carbon nanotube fabric, characterized by: include, The p-phenylenediamine, anhydrous ethanol and zinc chloride are mixed and stirred, and a p-benzoquinone ethanol solution is added, condensed and refluxed, centrifuged, and the precipitate is collected, dried and ground to prepare a p-benzoquinone p-phenylenediamine long-chain Schiff base; The multi-walled carbon nanotubes are dispersed in N,N-dimethylformamide, ultrasonicated, and p-benzoquinone p-phenylenediamine long-chain Schiff base is added and magnetically stirred to prepare a spraying liquid; The spraying liquid is evenly sprayed on the surface of the fabric, dried, and the spraying-drying steps are repeated 50 to 150 times to prepare a long-chain Schiff base coordinated carbon nanotube fabric.

2. The preparation method according to claim 1, wherein: The usage ratio of the p-phenylenediamine, anhydrous ethanol and zinc chloride is 0.01-0.02 mol: 20-40 ml: 0.15-0.3 g.

3. The preparation method according to claim 1, wherein: The dosage ratio of p-benzoquinone to ethanol in the p-benzoquinone ethanol solution is 0.01-0.02 mol: 20-40 ml, and the molar ratio of p-benzoquinone to p-phenylenediamine is 1:

1.

4. The preparation method according to claim 1, wherein: The multi-walled carbon nanotubes are dispersed in N,N-dimethylformamide, wherein the usage ratio of the multi-walled carbon nanotubes to the N,N-dimethylformamide is 0.5-2 g:100 mol.

5. The preparation method according to claim 1, wherein: The mass ratio of the multi-walled carbon nanotubes to the p-benzoquinone-p-phenylenediamine long-chain Schiff base is 1:2-8.

6. The preparation method according to claim 1, wherein: The temperature of the ultrasonic treatment is 30-40°C.

7. The preparation method according to claim 1, wherein: The magnetic stirring rate is 800 r / min.

8. The preparation method according to claim 1, wherein: The spraying liquid is evenly sprayed on the surface of the fabric, wherein the spraying thickness is controlled to be 0.5-2 mm.

9. Long-chain Schiff base synergistic carbon nanotube fabric prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the long-chain Schiff base synergistic carbon nanotube fabric as claimed in claim 9 in electromagnetic shielding fabric.

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