Preparation method and application of ultra-thin, high-strength and multifunctional carbon nanotube composite films

Abstract

The present invention discloses a preparation method and application of an ultra-thin, high-strength, and multifunctional carbon nanotube composite film. The method comprises: contacting the original carbon nanotube bundle with a protonating agent to transform it into an expanded state, and applying linear pressure to perform a protonation expansion and widening treatment; performing a first deprotonation treatment, wherein a portion of the adsorbed protonating agent is removed, and another portion of the adsorbed protonating agent is retained; performing a second deprotonation treatment, wherein a selected resin is dissolved in the second deprotonating agent, and the selected resin enters between the carbon nanotubes; and performing a heat treatment to obtain an ultra-thin, high-strength, and multifunctional carbon nanotube composite film. The present invention adopts a protonation expansion and ultra-thin widening treatment method to form an ultra-thin, ribbon-shaped expanded bundle, and then utilizes two de-expansion processes to make the resin entry process relatively gentler and more uniform. Finally, after heat treatment and shaping, a multifunctional carbon nanotube composite film with ultra-thinness, high orientation, and high uniformity is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon composite materials, and in particular to a preparation method and application of an ultra-thin, high-strength, multifunctional carbon nanotube composite film. Background Art

[0002] Similar to carbon fiber-resin composite materials, in the field of carbon nanotubes, the industry has gradually developed a variety of preparation methods for carbon nanotube-resin composite materials to achieve widespread application of carbon nanotube materials.

[0003] The existing preparation methods mainly include: (1) using carbon nanotube film impregnated with resin and multi-stage drawing to prepare carbon nanotube composite film. Although it can achieve the composite of carbon nanotubes and resin, due to poor orientation, insufficient uniformity, and non-density, it leads to poor mechanical properties and cannot be prepared continuously on a large scale; (2) using floating catalysis to prepare aerogel-like carbon nanotube aggregates. When the unshrinking carbon nanotube aggregates contact with the liquid phase system dissolved with resin and shrink and compact, the resin can be uniformly composited. However, since the carbon nanotube fibers directly prepared by the floating catalysis method have more internal pores, larger wrinkle density, and low orientation, they have poor mechanical properties and large thickness; (3) using the method of impregnating carbon nanotube fibers with post-treatment enhancement and winding to form a film to prepare carbon nanotube composite film. Since the thick carbon nanotube fibers enhanced by post-treatment have dense orientation, the resin cannot enter the fiber interior and can only accumulate on the surface, and can not achieve true uniform composite. Moreover, when the resin content is low, it cannot form a film, that is, it is impossible to make a carbon nanotube composite film with a low resin content.

[0004] The above preparation methods also have an obvious common defect, that is, the distribution of the resin in the carbon nanotube network is not uniform, and often has a tendency to concentrate toward the surface. Especially for the third technical solution, the resin is concentrated in large quantities near the surface area, and a uniform carbon nanotube-resin system is not formed. When preparing the stacked composite structural parts, it is easy to cause problems such as delamination or stress concentration, and the high toughness and high strength characteristics of the carbon nanotubes cannot be brought into play.

[0005] In general, the carbon nanotube composite films prepared by existing technologies have too many defects such as insufficient orientation, density, excessive thickness or wrinkles, as well as uneven dispersion of resin in the carbon nanotube system, making it impossible to achieve continuous large-scale preparation of high-strength ultra-thin carbon nanotube composite films. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a preparation method and application of an ultra-thin, high-strength, multifunctional carbon nanotube composite film.

[0007] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0008] In a first aspect, the present invention provides a method for preparing an ultra-thin, high-strength, multifunctional carbon nanotube composite film, comprising:

[0009] contacting the original carbon nanotube bundle with a protonating agent to transform it into an expanded state, and applying a radial linear pressure to the original carbon nanotube bundle in the expanded state to perform a protonation expansion and widening treatment to obtain an ultrathin widened body, wherein the protonating agent is adsorbed in the ultrathin widened body;

[0010] contacting the ultrathin widened body with a first deprotonating agent to perform a first deprotonation treatment, wherein a portion of the protonating agent adsorbed in the ultrathin widened body is removed and another portion of the protonating agent adsorbed is retained, thereby obtaining a de-expanded cluster body, wherein the degree of expansion of the de-expanded cluster body is lower than that of the ultrathin widened body, and the first deprotonating agent is still adsorbed in the de-expanded cluster body;

[0011] contacting the de-expanded cluster with a second deprotonating agent for a second deprotonation treatment, wherein a selected resin is dissolved in the second deprotonating agent, and during the second deprotonation treatment, the selected resin enters between the carbon nanotubes to obtain a resin composite, wherein the degree of expansion of the resin composite is lower than that of the de-expanded cluster, and the remaining protonating agent and the first deprotonating agent in the resin composite are removed;

[0012] The resin composite is heat-treated to remove the second deprotonating agent, thereby obtaining an ultra-thin, high-strength, and multifunctional carbon nanotube composite film.

[0013] In a second aspect, the present invention further provides a carbon nanotube composite material, which is formed by stacking and combining multiple layered units along the thickness direction, and the layered units include the ultra-thin, high-strength, multifunctional carbon nanotube composite film obtained by the above preparation method.

[0014] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least:

[0015] The technical solution provided by the present invention adopts a protonation expansion and ultra-thin widening treatment method to form an ultra-thin strip-shaped expanded cluster. Then, two de-expansion processes are used to first replace a portion of the protonating agent to adsorb a portion of the first deprotonating agent. Then, a second deprotonating agent dissolved with a resin is used to completely replace the remaining protonating agent and the first deprotonating agent. The resin incorporation process is relatively gentle and uniform. Finally, after heat treatment and shaping, a multifunctional carbon nanotube composite film with ultra-thin, high orientation and high uniformity is obtained. The laminated composite material prepared from the film has advanced properties such as high strength, high toughness and high uniformity.

[0016] The above description is only an overview of the technical solution of the present invention. In order to enable those skilled in the art to more clearly understand the technical means of this application and implement them according to the contents of the specification, the following is an explanation of the preferred embodiments of the present invention with detailed drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic structural diagram of a device for preparing an ultra-thin, high-strength, and multifunctional carbon nanotube composite film provided by a typical embodiment of the present invention;

[0018] Figure 2 This is a physical photo of an ultra-thin, high-strength, multifunctional carbon nanotube composite film provided by a typical embodiment of the present invention;

[0019] Figure 3 This is a low-magnification electron microscope photograph of a cross section of an ultra-thin, high-strength, multifunctional carbon nanotube composite film provided in a typical embodiment of the present invention;

[0020] Figure 4 This is a high-magnification electron microscope photograph of a cross section of an ultra-thin, high-strength, multifunctional carbon nanotube composite film provided in a typical embodiment of the present invention;

[0021] Figure 5 This is a surface electron microscope photograph of an ultra-thin, high-strength, multifunctional carbon nanotube composite film provided by a typical embodiment of the present invention;

[0022] Figure 6 This is a mechanical strength test diagram of an ultra-thin, high-strength, multifunctional carbon nanotube composite film provided in a typical embodiment of the present invention.

[0023] Explanation of the accompanying drawings: 1. Pay-off assembly; 2. Micro-comb assembly; 3. Lower traction roller; 4. Upper traction roller; 5. Expansion tank; 6. De-expansion tank; 7. Cleaning and resin compound tank; 8. Heat treatment assembly; 9. Take-up assembly. DETAILED DESCRIPTION

[0024] In view of the shortcomings of the prior art, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of the present invention. The following will further explain this technical solution, its implementation process and principles.

[0025] 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. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0026] Moreover, relational terms such as “first” and “second” are merely used to distinguish one component or method step from another with the same name, but do not necessarily require or imply any actual relationship or order between these components or method steps.

[0027] Existing carbon nanotube-resin preparation schemes make it difficult to achieve uniform compounding of resin and carbon nanotube bundles. The inventors believe that the reason is that the current preparation schemes lack control over the thickness or morphology of the carbon nanotube bundles. For example, in the case of a thin film impregnation compounding scheme, an overly thick film does not allow the resin to penetrate deep into the carbon nanotube network, which inevitably results in uneven distribution inside and outside. Another example is the impregnation compounding scheme using aerogel and a densified liquid containing dissolved resin. Although the distance between carbon nanotubes in the aerogel-state carbon nanotube aggregates is large, providing ample space for the entry of the resin, the shrinkage of the aerogel after encountering the liquid phase will produce a large number of wrinkles, and the resin will inevitably be uneven near the wrinkles, resulting in the resin in the final composite being not evenly distributed.

[0028] In applications such as the preparation of high-performance laminated composite structural parts, the uniformity of the resin distribution of the composite is a key factor affecting the properties of the final structural parts. If the distribution is uneven, it will lead to differences in bonding force and mechanical strength at different positions, resulting in problems such as slippage, delamination, and stress points, and loss of many properties such as mechanical strength. Therefore, the purpose of the present invention is to provide an ultra-thin, uniform, high-performance carbon nanotube composite film.

[0029] The method for controlling the thickness and morphology of carbon nanotube bundles can be achieved through the protonation expansion technology used in the inventors' previous research. The principle of its expansion can be referred to the existing published patent "Carbon Nanotube Bundles, Preparation Methods and Applications Thereof", but it is not limited to this. Numerous articles also provide relevant information on the protonation expansion of carbon nanotubes. After the protonation expansion, the present invention also applies radial pressure to spread the expanded body into a thin film in the width direction, thereby achieving ultra-thin morphology control and providing a basis for subsequent uniform resin compounding. At the same time, during the resin compounding process, the inventors also found that if the cleaning and replacement of the protonation reagent and the introduction of the resin are completed in one go, the rapid replacement rate often prevents the resin from fully entering and diffusing between the carbon nanotubes, which can also lead to deformation of the carbon nanotube aggregates and uneven resin distribution. Therefore, the present invention specifically arranges two deprotonation processes and simultaneously introduces the resin during the latter deprotonation, ultimately obtaining a highly uniform ultra-thin carbon nanotube-resin composite film.

[0030] Based on the above technical ideas, a first aspect of an embodiment of the present invention provides a method for preparing an ultra-thin, high-strength, multifunctional carbon nanotube composite film, which comprises the following steps:

[0031] contacting the original carbon nanotube bundle with a protonating agent to transform it into an expanded state, and applying a radial linear pressure to the original carbon nanotube bundle in the expanded state to perform a protonation expansion and widening treatment to obtain an ultrathin widened body, wherein the protonating agent is adsorbed in the ultrathin widened body;

[0032] contacting the ultrathin widened body with a first deprotonating agent to perform a first deprotonation treatment, wherein a portion of the protonating agent adsorbed in the ultrathin widened body is removed and another portion of the protonating agent adsorbed is retained, thereby obtaining a de-expanded cluster body, wherein the degree of expansion of the de-expanded cluster body is lower than that of the ultrathin widened body, and the first deprotonating agent is still adsorbed in the de-expanded cluster body;

[0033] contacting the de-expanded cluster with a second deprotonating agent for a second deprotonation treatment, wherein a selected resin is dissolved in the second deprotonating agent. During the second deprotonation treatment, the selected resin enters between the carbon nanotubes to obtain a resin composite, wherein the degree of expansion of the resin composite is lower than that of the de-expanded cluster, and the remaining protonating agent and the first deprotonating agent in the resin composite are largely and relatively completely removed;

[0034] The resin composite is heat-treated to remove the second deprotonating agent, and the resin is solidified or the morphology of the carbon nanotube-resin composite is fixed to obtain an ultra-thin, high-strength, multifunctional carbon nanotube composite film.

[0035] In the above technical solution, the carbon nanotube network is shaped based on ultrathin expansion and widening, and then a first deprotonation treatment is performed to displace a portion of the protonating agent, but not all of it. At this time, the degree of expansion is reduced and a portion of the first deprotonating agent is adsorbed in the aggregate. This process does not yet introduce the resin but provides a basis for the subsequent uniform and gentle introduction of the resin. Then, a second deprotonating agent that dissolves the resin is used to further uniformly and relatively thoroughly replace the first deprotonating agent and the remaining protonating agent (in actual conditions, a small amount may remain and cannot be completely removed 100%). This process achieves uniform introduction of the resin to obtain a resin composite. Finally, through heat treatment, the second protonating agent is removed (and the small amount of residual protonating agent and the first deprotonating agent that were not completely removed in the previous step are also removed) and the resin composite is shaped, resulting in an ultrathin, high-strength, and multifunctional carbon nanotube composite film.

[0036] If the resin is added only to the protonating agent or only to the first deprotonating agent, in the former, the resin enters the expansion body too early, and the thickness of the expansion body is very thin. Therefore, a large amount of reverse precipitation will occur during the subsequent treatment process, and uniform and high-content composite cannot be achieved. At the same time, the residual protonating agent will also affect the molecular chain of the resin, reducing the composite strength. In the latter, the first deprotonating agent cannot completely replace the protonating agent, so the amount of resin introduced is insufficient, and the effect of completely uniform introduction cannot be achieved, and the preparation of ultra-thin and highly uniform composite films cannot be achieved.

[0037] Furthermore, using only the first deprotonating solvent can result in incomplete proton removal, affecting the mechanical and electrical properties of the bundle. Using only the second deprotonating agent can not only hinder resin incorporation but also lead to violent chemical reactions within the bundle, resulting in numerous defects and disrupting the internal structure, thus affecting its mechanical, electrical, and thermal properties.

[0038] In the above technical solution, it is critical to achieve ultra-thin widening during protonation expansion and resin introduction during secondary deprotonation during the deprotonation process. Regarding the two deprotonation processes, in some embodiments, the first deprotonating agent is compatible with the protonating agent, the second deprotonating agent is compatible with the first deprotonating agent, and the second deprotonating agent is reactive with the protonating agent.

[0039] Compatibility of the two deprotonating agents is essential for achieving simultaneous and uniform reagent replacement and introduction into the resin. Furthermore, a preferred embodiment of the present invention utilizes the difference in deprotonation ability (which can be understood as a difference in solubility for the protonating agent) between the two deprotonating agents to initially utilize a first deprotonating agent with a slightly weaker deprotonation ability to relatively slowly remove a portion of the protonating agent, followed by a second deprotonating agent with a stronger deprotonation ability to more thoroughly replace the remaining protonating agent and the first deprotonating agent, thereby achieving relatively uniform and deep introduction into the resin and uniform recombination. Preferably, the second deprotonating agent has a stronger ability to remove the protonating agent than the first deprotonating agent. In most cases, the second deprotonating agent has a certain degree of reactivity with the protonating agent.

[0040] Regarding more specific reagent selection, in some embodiments, the first deprotonating agent may include any one of chloroform, carbon tetrachloride, and nitrobenzene, or a combination of two or more thereof; the second deprotonating agent may include any one of acetone, N-methylpyrrolidone, dimethylformamide, and dimethyl sulfoxide, or a combination of two or more thereof.

[0041] As for the resin, in some preferred embodiments, the selected resin is a viscous polymer resin, including any one or a combination of two or more of benzoxazine resin, epoxy resin, polyimide, polybenzimidazole, polyvinylidene fluoride, polyvinyl pyrrolidone, and polyvinyl alcohol.

[0042] More specifically, in some embodiments, the mass fraction of the selected resin in the second deprotonating agent is 1%-98%.

[0043] Furthermore, based on the process and mechanism described above, another notable feature of the preparation method proposed by the present invention is that, in some embodiments, the protonating agent and the first deprotonating agent do not contain a polymer. This is to prevent the polymer from prematurely entering the expanded carbon nanotube body and affecting the subsequent uniform resin incorporation process.

[0044] Regarding the expansion and widening process, in some embodiments, the linear pressure is applied in the following manner:

[0045] An axial stretching force is applied to the expanded raw carbon nanotube bundle, and a roller extending in a direction intersecting the axial direction is used to contact the raw carbon nanotube bundle. In a specific embodiment, upper and lower pulling rollers, alternately arranged on opposite sides of a plane, can be used to coordinate with each other, so that the expanded bundle alternately wraps around the upper and lower stretching rollers during its movement, thereby achieving the application of linear pressure.

[0046] Specifically in some embodiments, the angle between the expanded original carbon nanotube bundle and the roller axis is 30-130°.

[0047] In some embodiments, the pay-off rate of the raw carbon nanotube bundle is 0.01-100 m / h.

[0048] In some embodiments, the degree of orientation can also be improved by expansion stretching. Of course, this is an existing technical means. Generally, the stretching rate of the original carbon nanotube bundle caused by the stretching force is 10-50%.

[0049] In addition, the above technical solution is generally applicable to multiple carbon nanotube fibers, which can be fused during the expansion and widening process, and the width of the final composite film can be adjusted by adjusting the number of fibers. That is, in some embodiments, the number of carbon nanotube fibers in the original carbon nanotube bundle is multiple, and the multiple carbon nanotube fibers are combed into a linear arrangement before contacting the protonating agent, and the arrangement direction is in the same plane as the extension direction of the roller.

[0050] Of course, it is not limited to this. If the width of the final composite film is not required to be high, for example, a narrow strip-shaped film is desired, then one original carbon nanotube fiber can be prepared, and the process flow and mechanism of action are the same.

[0051] In order to realize the above-mentioned preparation method, a typical embodiment of the present invention adopts a preparation device of an ultra-thin, high-strength and multifunctional carbon nanotube composite film, which can be seen in Figure 1 As shown, the device includes:

[0052] Pay-off assembly 1: The pay-off assembly consists of multiple pay-off shafts, each of which can pay out a single strand of carbon nanotube fiber or a multi-strand carbon nanotube bundle. All pay-off rates are controlled to be V1, and the pay-off rate range is 0.01-100 m / h.

[0053] Microcomb Assembly 2: Utilizing comb teeth, multiple fiber strands are precisely arranged and guided, resulting in a planar layout. This ensures that each fiber is positioned and oriented consistently, preventing crossover during the towing process and achieving uniform, directional bundling. The microcomb assembly features multiple precise microgrooves, each capable of passing one or more fiber strands. The width and spacing of the microgrooves are adjustable, allowing the microcomb assembly to uniformly tow multiple fiber strands, increasing the uniformity of the tow's expansion within the expansion slot. By adjusting the microgroove width, spacing, and number of fiber strands on the microcomb assembly, continuous and controllable preparation of carbon nanotube films of varying widths is possible.

[0054] Lower traction roller 3: introduces the tow into each solution tank or heat treatment component. The roller can actively feed the wire, passively feed the wire, or not feed the wire. Its equivalent circle diameter ranges from 1 to 100 mm.

[0055] Upper traction roller 4: cooperates with the lower traction roller 3 to make the expanded tow form an upper and lower broken line path, so that the tow is subjected to a force perpendicular to the axial direction of the traction shaft in the solution, further widening the tow;

[0056] Expansion tank 5: Uses a protonating agent to expand the fibers within the solution, widening, stretching, and fusing them. The expansion tank can be made of one or more materials, such as quartz, polytetrafluoroethylene, or other materials coated with quartz or polytetrafluoroethylene. The protonating agent can be one or more of chlorosulfonic acid, methanesulfonic acid, and fuming sulfuric acid.

[0057] De-expansion tank 6: Performs a first deprotonation step to reduce the fiber's expansion within the expansion tank. The tank can be made of one or more materials such as quartz, polytetrafluoroethylene, or other materials coated with quartz or polytetrafluoroethylene. The first deprotonation agent can be one or more of chloroform, carbon tetrachloride, and nitrobenzene.

[0058] Cleaning and Resin Compounding Tank 7: This tank performs thorough replacement cleaning while uniformly compounding the resin with the carbon nanotube film. The second deprotonating agent used to dissolve the resin further removes any residual protonating agent and the first deprotonating agent within the fiber bundle. The material used can be one or more of quartz, polytetrafluoroethylene, or other materials coated with quartz or polytetrafluoroethylene. The dissolved resin can be a viscous polymer resin, including any one or a combination of two or more of benzoxazine resin, epoxy resin, polyimide, polybenzimidazole, polyvinylidene fluoride, polyvinyl pyrrolidone, and polyvinyl alcohol. The solvent used to dissolve the resin can be one or more of acetone, N-methylpyrrolidone, dimethylformamide, and dimethyl sulfoxide.

[0059] Heat treatment component 8: used to completely remove the liquid residue in the thin film composite. If a thermosetting resin is selected, the resin in the composite film can be pre-cured at the same time (pre-curing occurs when a thermosetting resin is selected as the selected resin. If a thermoplastic resin is selected, the process mainly removes the residual liquid phase) to obtain a structurally stable ultra-thin high-strength carbon nanotube composite film. The annealing temperature range is generally 100-550°C.

[0060] The take-up component 9 is a collecting end for the composite film, which collects the obtained composite film and provides a stretching force during the processing. The collection speed V2 ranges from 0.01 to 100 m / h, where V1 ≤ V2 to achieve no stretching or a certain degree of stretching. Of course, whether to stretch is not the key to the present invention, but lies in the combination of ultra-thin widening and secondary resin introduction.

[0061] As a typical application of the above technical solution, an embodiment of the present invention also provides a carbon nanotube composite material, which is formed by multiple layered units stacked and combined along the thickness direction, and the layered units include an ultra-thin, high-strength, multifunctional carbon nanotube composite film obtained by the preparation method provided in any of the above embodiments.

[0062] The technical solution of the present invention is further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0063] The following embodiments provide ultrathin, high-strength, and multifunctional carbon nanotube composite films, as well as their preparation methods and applications. The general process involves: after multiple strands of carbon nanotube fibers are evenly combined by micro-combing, they are then sequentially stretched to ultrathin thickness by rollers using an expansion solution under inert atmosphere conditions (primarily to prevent the influence of moisture in the air on the composite process), followed by removal of the protonated reagent with the expansion solution, uniform composite and cleaning with a resin solution, and finally cross-linking, curing, and densification through high-temperature annealing. The resin solution is a cleaning solvent containing a large amount of resin. The resin is introduced after the carbon nanotube fibers have expanded and fused but before they are fully densified, enabling uniform composite bonding with a high content of the selected resin, and the resin content is controllable. The resulting product is generally less than 5 μm thick and can typically have a strength greater than 5 GPa.

[0064] Specifically, the various embodiments provided by the present invention are prepared using the following process:

[0065] a. Selecting the number of carbon nanotube fiber rolls and the number of carbon nanotube fiber strands per roll based on the desired film width, and fixing the selected carbon nanotube fiber rolls on a pay-off device;

[0066] b. Selecting the width and spacing of the microgrooves between the comb teeth in the microcomb assembly based on the number of rolls and the number of strands in each roll of carbon nanotube fiber, and passing the corresponding microgrooves according to the spinning position of each roll of carbon nanotube fiber;

[0067] c. Then, under the folded line traction of the upper traction roller and the lower traction roller, it passes through the expansion tank, de-expansion tank, cleaning and resin compound tank, and heat treatment assembly, and is fixed on the empty reel of the take-up assembly;

[0068] d. Determine the selected resin (hereinafter referred to as "solute") and its concentration, add the second deprotonating agent, the first deprotonating agent, and the protonating agent to each solution tank, and then turn on the annealing furnace and raise the temperature to the target temperature;

[0069] e. Set the traction speed of the pay-off device, the collecting device and all active traction wheels, where the traction speed of the pay-off device is ≤ the traction speed of the winding device;

[0070] f. Simultaneously turn on the unwinding device, the collecting device, and all active traction device switches, and simultaneously carry out the carbon nanotube fiber bundle fusion, drawing, widening, double deprotonation, resin compounding, and heat treatment shaping process steps.

[0071] Example 1

[0072] This example used 10 rolls of 10 carbon nanotube fibers. Each of the 10 microgrooves on the microcomb assembly had a width of 0.2 mm and a spacing of 0.3 mm. The protonating agent was chlorosulfonic acid, the primary deprotonating agent was chloroform, the secondary deprotonating solvent was N-methylpyrrolidone, the solute was polybenzimidazole at a concentration of 10 wt%, and the draw ratio was 30%. The resulting composite film had a width of 14 mm, a thickness of 2 μm, and a resin content of 10.08%.

[0073] The actual photo of the ultra-thin, high-strength, multifunctional carbon nanotube composite film prepared in this example is shown in the figure. Figure 2 As shown, it is cut radially and its cross section is observed. The cross-sectional morphology at different magnifications is as follows: Figure 3 and Figure 4 Its surface morphology is shown in Figure 5 shown.

[0074] It can be seen that the ultra-thin, high-strength, multifunctional carbon nanotube composite film obtained in this embodiment is thin and uniform in thickness, without wrinkles, damage, particles and other undesirable phenomena, and the distribution of resin in the carbon nanotube bundles is very uniform. The ultra-thin, high-strength, multifunctional carbon nanotube composite film obtained in this embodiment was subjected to a tensile test, and the results are as follows: Figure 6 As shown, it can be seen that the ultra-thin, high-strength, multifunctional carbon nanotube composite film has excellent properties of high strength and high toughness.

[0075] Example 2

[0076] This example used 10 rolls of 30 carbon nanotube fibers. Each of the 10 microgrooves on the microcomb assembly had a width of 0.6 mm and a spacing of 0.3 mm. The protonating agent was chlorosulfonic acid, the primary deprotonating agent was carbon tetrachloride, the secondary deprotonating solvent was dimethylformamide, the solute was polyvinylidene chloride at a concentration of 30 wt%, and the draw ratio was 20%. The resulting composite film had a width of 40 mm, a thickness of 2.1 μm, and a resin content of 23.8%.

[0077] Example 3

[0078] This example used 20 rolls of 30 carbon nanotube fibers. The microcomb assembly had 20 microgrooves, each 0.6 mm wide and 0.3 mm apart. The protonating agent was methanesulfonic acid, the primary deprotonating agent was nitrobenzene, the secondary deprotonating solvent was acetone, the solute was epoxy resin at a concentration of 50 wt%, and the draw ratio was 18%. The resulting composite film was 90 mm wide, 2.5 μm thick, and had a resin content of 33.9%.

[0079] Example 4

[0080] This example used 30 rolls of 50 carbon nanotube fibers. The microcomb assembly had 30 microgrooves, each 1 mm wide and 0.3 mm apart. The protonating agent was fuming sulfuric acid, the first deprotonating agent was carbon tetrachloride, the solute was N-methylpyrrolidone, the concentration of benzoxazine resin was 98 wt%, and the draw ratio was 16%. The resulting composite film had a width of 150 mm, a thickness of 2.8 μm, and a resin content of 37.8%.

[0081] Comparative Example 1

[0082] This comparative example is substantially the same as Example 1, except that:

[0083] The resin concentration in the cleaning and resin compounding tank was halved to 5%, and a portion of the resin was added to the first deprotonating agent in the deswelling tank at a concentration of 5%.

[0084] The obtained product is a strip-shaped product with uneven compounding and low resin content, and the thickness is also uneven, with obvious wrinkles, lumps and other defects.

[0085] Comparative Example 2

[0086] This comparative example is substantially the same as Example 1, except that:

[0087] The resin in the cleaning and resin compounding tank is removed, and the resin at an equal concentration is added to the first deprotonating agent in the deswelling tank.

[0088] The obtained product is still a strip-shaped product with uneven compounding and low resin content, and the thickness is also uneven, with obvious wrinkles, lumps and other defects.

[0089] Comparative Example 3

[0090] This comparative example is substantially the same as Example 1, except that:

[0091] The resin concentration in the cleaning and resin compound tank was halved to 5%, and a portion of the resin was added to the protonating agent in the expansion tank at a concentration of 5%.

[0092] The obtained product is still a strip-shaped product with uneven compounding and low resin content, and the thickness is also uneven, with obvious wrinkles, lumps and other defects.

[0093] According to the above comparative examples, it can be found that in order to achieve ultra-thin and uniform high-density resin composite, resin cannot be introduced into the protonating agent and the first deprotonating agent, and the resin can only be introduced in a targeted manner during the cleaning and replacement process of the second protonating agent.

[0094] Comparative Example 4

[0095] This comparative example is substantially the same as Example 1, except that:

[0096] The expansion tank is eliminated and the expanded fiber bundle is directly introduced into the cleaning and resin compound tank.

[0097] In the obtained product, the resin cannot be evenly dispersed in the carbon nanotube bundle, but is less distributed in the central core area and more distributed in the area near the edge surface. This is because the solvent exchange rate is too fast during direct deprotonation without undergoing two deprotonations. The resin does not have time to penetrate deeply into the fiber bundle before the liquid phase replacement process is completed, which is similar to the retention of molecules by a chromatographic column, and the resin is retained near the surface.

[0098] Based on the above embodiments and comparative examples, it can be clearly seen that the embodiments of the present invention are based on a method for preparing highly oriented ultra-thin and widened carbon nanotube fibers. A micro-comb is introduced during fiber bundle formation to improve the uniformity of expansion and fusion of multiple strands of fibers. By regulating the number of fiber rolls and strands, the number and width of microgrooves of the micro-comb, continuous large-scale preparation of high-strength ultra-thin carbon nanotube composite films of different widths is achieved. Resin is introduced after expansion and before complete densification to achieve uniform resin compounding. By regulating the concentration of the resin solution, continuous preparation of high-strength ultra-thin carbon nanotube composite films with different resin contents can be achieved. This method can continuously and synchronously achieve the effects of multi-strand fiber bundle formation, uniform fusion, stretching orientation, ultra-thinness, uniform compounding of high-concentration resins, etc., which is conducive to the large-scale preparation of ultra-thin and high-strength carbon nanotube composite films, and the composite films have excellent multifunctionality such as ultra-thinness, high strength, high temperature resistance, electromagnetic shielding, electrical conductivity, thermal conductivity, etc., and the film width and resin content are adjustable.

[0099] The present invention has the following advantages: (1) micro-combs are introduced during fiber bundle formation to improve the uniformity of expansion and fusion of multiple fiber strands, and continuous large-scale preparation of high-strength ultra-thin carbon nanotube composite films of different widths can be achieved by regulating the number of fiber strands and the width of the micro-combs. (2) Resin is introduced after expansion but before complete densification to achieve uniform resin compounding, and continuous preparation of high-strength ultra-thin carbon nanotube composite films with different resin contents can be achieved by regulating the concentration of the resin solution. (3) This method can continuously and synchronously achieve the effects of fiber bundle formation, uniform fusion, stretching orientation, ultra-thinness, uniform compounding of high-concentration resins, etc. of multiple fiber strands, which is conducive to the large-scale preparation of ultra-thin high-strength carbon nanotube composite films. (4) This method can realize the integration of composite films with excellent multifunctionality such as ultra-thinness, high strength, high temperature resistance, electromagnetic shielding, electrical conductivity, and thermal conductivity, and has great application prospects in the fields of aerospace, national defense, and military industry.

[0100] It should be understood that the above embodiments are merely illustrative of the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent variations or modifications made in accordance with the spirit and substance of the present invention are intended to be encompassed within the scope of protection of the present invention.

Claims

1. A method for preparing an ultra-thin, high-strength, multifunctional carbon nanotube composite film, characterized in that: include: contacting the original carbon nanotube bundle with a protonating agent to transform it into an expanded state, and applying a radial linear pressure to the original carbon nanotube bundle in the expanded state to perform a protonation expansion and widening treatment to obtain an ultrathin widened body, wherein the protonating agent is adsorbed in the ultrathin widened body; contacting the ultrathin widened body with a first deprotonating agent to perform a first deprotonation treatment, wherein a portion of the protonating agent adsorbed in the ultrathin widened body is removed and another portion of the protonating agent adsorbed is retained, thereby obtaining a de-expanded cluster body, wherein the degree of expansion of the de-expanded cluster body is lower than that of the ultrathin widened body, and the first deprotonating agent is still adsorbed in the de-expanded cluster body; contacting the de-expanded cluster with a second deprotonating agent for a second deprotonation treatment, wherein a selected resin is dissolved in the second deprotonating agent, and during the second deprotonation treatment, the selected resin enters between the carbon nanotubes to obtain a resin composite, wherein the degree of expansion of the resin composite is lower than that of the de-expanded cluster, and the remaining protonating agent and the first deprotonating agent in the resin composite are removed; The resin composite is heat-treated to remove the second deprotonating agent, thereby obtaining an ultra-thin, high-strength, and multifunctional carbon nanotube composite film.

2. The preparation method according to claim 1, characterized in that The first deprotonating agent is compatible with the protonating agent, the second deprotonating agent is compatible with the first deprotonating agent, and the second deprotonating agent is reactive with the protonating agent.

3. The preparation method according to claim 2, characterized in that The first deprotonating agent includes any one of chloroform, carbon tetrachloride, and nitrobenzene, or a combination of two or more thereof; the second deprotonating agent includes any one of acetone, N-methylpyrrolidone, dimethylformamide, and dimethyl sulfoxide, or a combination of two or more thereof.

4. The preparation method according to claim 3, characterized in that The selected resin is a viscous polymer resin, including any one or a combination of two or more of benzoxazine resin, epoxy resin, polyimide, polybenzimidazole, polyvinylidene fluoride, polyvinyl pyrrolidone, and polyvinyl alcohol.

5. The preparation method according to any one of claims 1 to 4, characterized in that In the second deprotonating agent, the mass fraction of the selected resin is 1%-98%.

6. The preparation method according to claim 1, characterized in that The protonating agent and the first deprotonating agent do not contain a polymer.

7. The preparation method according to claim 1, characterized in that The linear pressure is applied in the following ways: An axial tensile force is applied to the expanded raw carbon nanotube bundle, and a roller extending in a direction intersecting the axial direction is used to abut against the raw carbon nanotube bundle.

8. The preparation method according to claim 7, characterized in that The angle between the expanded original carbon nanotube bundle and the roller is 30-130°; and / or, the pay-off rate of the original carbon nanotube bundle is 0.01-100 m / h; And / or, the stretching rate of the original carbon nanotube bundle caused by the stretching force is 10-50%.

9. The preparation method according to claim 7, characterized in that The number of carbon nanotube fibers in the original carbon nanotube bundle is multiple, and the multiple carbon nanotube fibers are combed into a linear arrangement before contacting the protonation agent, and the arrangement direction is in the same plane as the extension direction of the roller, and the multiple carbon nanotube fibers are fused into one during the protonation expansion and widening treatment.

10. A carbon nanotube composite material, characterized in that: The carbon nanotube composite material is formed by stacking and combining a plurality of layered units along the thickness direction, and the layered units include an ultra-thin, high-strength, and multifunctional carbon nanotube composite film prepared by the preparation method according to any one of claims 1 to 9.

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