Drawing enhancement method and system for carbon nanotube fibers

Abstract

The application discloses a kind of carbon nanotube fiber drawing enhancement method and system.The drawing enhancement method includes: providing carbon nanotube fiber, carbon nanotube fiber is twisted state;Carbon nanotube fiber is cabled and is treated, and fiber bundle is obtained;Protonation drawing and coagulation bath treatment are carried out to fiber bundle, and precursor fiber is obtained;Protonation reagent and / or coagulation bath reagent in precursor fiber are removed, and carbon nanotube reinforced fiber is obtained.The drawing enhancement method provided by the application is twisted and is cabled and is treated, after the internal each expansion fiber edge shape of fiber bundle is expanded by strong acid protonation, adaptive effect is generated;During drawing process, make stress more evenly be applied on each fiber, improve the stability in the process of fiber drawing, to realize higher drawing rate and drawing rate, finally significantly improve the mechanical strength and consistency of reinforced fiber, and bring very excellent continuity, very beneficial to the application of carbon nanotube fiber.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inorganic carbon materials or high-performance fibers, and particularly relates to a drawing enhancement method and system for carbon nanotube fibers. BACKGROUND

[0002] Carbon nanotube fibers (CNTF) are fibrous materials assembled by a large number of carbon nanotubes. The constituent unit carbon nanotube itself has very excellent mechanical properties, and the tensile breaking strength and tensile modulus thereof are more than 100 GPa and 1000 GPa, respectively. However, the fibrous macrobody of carbon nanotubes is difficult to overcome the influence of a series of factors such as structural defects in the preparation and assembly process, and finally makes the mechanical properties of carbon nanotube fibers far lower than those of the molecular-level carbon nanotubes themselves.

[0003] For example, the commonly used floating catalytic method has low cost and high production capacity, but the prepared fibers have the characteristics of low density, poor internal structure orientation and high impurity content, which affects the final strength of the fibers.

[0004] Subsequent drawing treatment of carbon nanotube fiber filaments is one of the most effective methods for enhancing the mechanical properties of fibers. By applying appropriate drawing action to the fibers, the internal structure orientation and density of the fibers can be controlled to achieve mechanical enhancement of the carbon nanotube fibers.

[0005] Some prior art such as Chinese invention patent with publication number CN112359441A uses the heat generated by the electric current to soften the polymer into a high-elasticity state, and then reorients and densifies the carbon nanotube / polymer composite fiber through drawing.

[0006] In addition, some other prior art uses the protonation effect of strong acid to make the carbon nanotube fiber swell and the internal tube interaction force weaken, thereby achieving effective drawing enhancement (for example, Jaegeun Lee, et al., Nature Communications, 2019, 10 2962, and Chinese invention patent with publication number CN114672899A). The continuous post-treatment enhancement of the fiber is realized based on the assistance of strong acid.

[0007] However, the mechanical strength of the fibers treated by the current drawing enhancement method is still insufficient, and the difference between the multiple strengthened fibers is very obvious, and the consistency is poor, which greatly limits the application of carbon nanotube fibers as high-performance fibers.

[0008] In addition, the current technical solution cannot achieve long continuity when drawing the fibers, and fiber breakage often occurs, which greatly increases the preparation cost of the fibers and reduces the production efficiency. SUMMARY

[0009] In view of the deficiencies of the prior art, the present application aims to provide a drawing and strengthening method and system for carbon nanotube fibers.

[0010] To achieve the above-mentioned objects, the present application employs the following technical solutions.

[0011] In a first aspect, the present application provides a drawing and strengthening method for carbon nanotube fibers, which comprises the following steps:

[0012] providing carbon nanotube fibers in a twisted state;

[0013] plying the carbon nanotube fibers to obtain a fiber bundle;

[0014] protonating and drawing the fiber bundle and treating it in a coagulation bath to obtain a precursor fiber;

[0015] removing the protonating agent and / or the coagulation bath agent from the precursor fiber to obtain a carbon nanotube reinforced fiber.

[0016] In a second aspect, the present application further provides a drawing and strengthening system for carbon nanotube fibers, which comprises the following modules:

[0017] a plying module for plying carbon nanotube fibers in a twisted state to obtain a fiber bundle;

[0018] a drawing module for protonating and drawing the fiber bundle and treating it in a coagulation bath to obtain a precursor fiber;

[0019] a post-processing module for removing the protonating agent and / or the coagulation bath agent from the precursor fiber to obtain a carbon nanotube reinforced fiber.

[0020] Based on the above technical solutions, the present application has at least the following advantages over the prior art:

[0021] The drawing and strengthening method provided by the present application involves twisting and plying the carbon nanotube fibers, and then drawing the plied fiber bundle with the assistance of a strong acid. After the fiber bundle is protonated and expanded by the strong acid, the edges of the expanded fibers in the fiber bundle adapt to each other, the gaps between the plied fibers are filled, and the effective contact between the fibers is increased. During the drawing process, the effective contact between the fibers can transmit the drawing stress to each other, so that the stress is more uniformly applied to each fiber, thereby greatly improving the stability of the fibers during the drawing process, and achieving a higher drawing speed and drawing rate. Finally, the mechanical strength and consistency of the reinforced fibers are significantly improved, and very excellent continuity is achieved, which is very beneficial to the application of carbon nanotube fibers.

[0022] In addition, the method provided by the application also brings very significant preparation efficiency advantages, which are not only the improvement of batch processing quantity brought by the plying of multiple fibers and drawing together, but also the advantages brought by the high continuity.

[0023] The above description is only a summary of the technical solutions of the application. In order to enable those skilled in the art to more clearly understand the technical means of the present application and can be implemented according to the content of the description, the following is a preferred embodiment of the application and the detailed description of the drawings as follows. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a process schematic diagram of the drawing enhancement method provided by a typical embodiment of the application;

[0025] Figure 2a is a test diagram of the relationship between the mechanical properties of the carbon nanotube raw fiber under different first twisting angles provided by a typical embodiment of the application;

[0026] Figure 2b is a microscopic test photo of the carbon nanotube raw fiber under different first twisting angles provided by a typical embodiment of the application;

[0027] Figure 3 is a surface electron microscope photo of the carbon nanotube reinforced fiber provided by a typical comparative embodiment of the application;

[0028] Figure 4 is a surface electron microscope photo of the carbon nanotube reinforced fiber provided by a typical embodiment of the application;

[0029] Figure 5 is a mechanical property and consistency comparison test diagram of the carbon nanotube reinforced fiber provided by a typical embodiment and a comparative embodiment of the application. DETAILED DESCRIPTION

[0030] In view of the deficiencies in the prior art, the present inventors have long studied and practiced to come up with the technical solutions of the present application. The technical solutions, implementation process and principles will be further explained as follows.

[0031] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, however, the present application can also be implemented in other ways different from those described herein, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0032] Moreover, the relationship terms such as "first" and "second" are only used to distinguish one from another with the same name of components or method steps, and do not necessarily require or imply any such actual relationship or order between the components or method steps.

[0033] The current existing means for drawing enhancement of carbon nanotube fibers has the following shortcomings:

[0034] (1) Most of the existing enhancement means has low processing efficiency and short single processing length, about 10-20 cm, which cannot realize batch processing enhancement.

[0035] (2) Some continuous drawing enhancement means has poor continuity, especially for strong acid assisted drawing process. Under the protonation of strong acid, the inter-tube spacing of the fiber increases, the van der Waals force weakens, and the overall mechanical strength of the fiber basically loses its original mechanical strength. Although the above protonation can achieve a higher draw ratio of carbon nanotube fibers, it also weakens the ability of the fiber to resist external stress, resulting in easy breakage of the fiber during the drawing process, and cannot realize stable continuous post-processing enhancement.

[0036] (3) The mechanical strength of the fiber obtained by the current drawing method is still insufficient, and the fiber consistency is poor.

[0037] In view of the above shortcomings, the main purpose of the present application is to provide a kind of carbon nanotube fiber efficient post-processing enhancement method, in some specific examples, first by the twist treatment to the original silk prepared by floating catalytic method, and through subsequent drying process to the twist state is fixed, then the twisted original silk is cabled. Subsequently, through the protonation of strong acid, the twisted cabled fiber is expanded to apply a higher draw ratio, so that the internal structure of the carbon nanotube fiber is reoriented, and through subsequent cleaning and annealing treatment, finally realize efficient continuous processing of fiber. When drawing in strong acid by cabling the fibers, due to the self-adaptive effect of the edge shape of the fibers, the interstitial space of the cabled fibers is filled, and the effective contact between the fibers is increased. During the drawing process, the drawing stress can be shared by the fibers, so that the drawing force is more evenly applied to each fiber, which is the key to achieving a higher draw ratio in the present application. In addition, after cabling, the fiber is drawn in strong acid and then enters the coagulation bath to realize deprotonation. The concentration difference causes the fibers in the cabled fiber to shrink, and due to the radial shrinkage of the twisted fibers, each single fiber can be separated, and finally the efficient batch post-processing enhancement of carbon nanotube fibers is realized.

[0038] Therefore, referring to Figure 1 , the present application embodiment first provides a kind of drawing enhancement method of carbon nanotube fiber, it includes the following steps:

[0039] provide carbon nanotube fiber, the carbon nanotube fiber is twisted state.

[0040] the carbon nanotube fiber is cabled, and a fiber bundle is obtained.

[0041] The fiber bundle is subjected to protonation drafting and coagulation bath treatment to obtain a precursor fiber.

[0042] The protonation agent and / or coagulation bath agent in the precursor fiber are removed to obtain a carbon nanotube reinforced fiber.

[0043] As some typical application examples of the above technical solution, firstly, the wet fiber filaments grown by the floating catalysis method can be subjected to twisting treatment, then the twisted state of the fiber is solidified by drying, and the twisted fiber is plying. Finally, the twisted fiber after plying is subjected to continuous drafting and reinforcement by means of chlorosulfonic acid assisted drafting, wherein the continuous drafting and reinforcement system comprises a winding end, a drafting end, a cleaning end, and a winding end. The subsequent drafting and reinforcement treatment of the fiber after plying can greatly increase the fiber processing capacity, and the drafting after plying can improve the continuity, thereby realizing efficient post-treatment reinforcement of the fiber.

[0044] The carbon nanotube fiber as the raw material for subsequent plying and drafting treatment can be directly purchased as twisted fiber, or can be prepared by oneself, for example, the following carbon nanotube raw fiber is purchased and then subjected to twisting treatment, or the carbon nanotube raw fiber is prepared by oneself and then subjected to twisting treatment. That is, the preparation process exemplarily provided by the present application can be prepared by one producer, or can be dispersedly performed by multiple producers to perform different steps, and even the fiber bundle after plying can be prepared by one producer, and then transferred to another producer in various forms for subsequent treatment. Such treatment mode also belongs to the protection scope of the present application.

[0045] In some embodiments, the carbon nanotube fiber is obtained by twisting treatment of a carbon nanotube raw fiber.

[0046] In some embodiments, the first twisting angle of the carbon nanotube fiber can be preferably 5-35°.

[0047] In some embodiments, the diameter of the carbon nanotube fiber can be preferably 10-50 μm.

[0048] A very important point is that in the technical solution provided by the present application, twisting and plying jointly act. In the protonation drafting process, the fiber will swell due to protonation, and if appropriate twisting treatment is not matched, the swelled multi-strand fiber is prone to surface adhesion (which is an inevitable phenomenon caused by the high specific surface area and high flexibility and entanglement ability of carbon nanotubes), which on one hand makes it difficult to separate the multi-strand fiber after treatment, limiting the application scenarios, and on the other hand, the adhesion between each other significantly affects the sharing of the drafting stress between the fibers, and even due to the adhesion, part of the weaker fibers are damaged, greatly affecting the mechanical strength and consistency level of the fiber.

[0049] And combined with the appropriate twist, so that even if the expansion occurs between the plurality of fibers, it can have a certain "cohesion", that is, the twist overcomes the expansion effect of a certain degree of shrinkage trend, which makes it difficult for fibers to stick together, and a certain degree of free sliding, not easy to occur surface damage and make the draft stress can be unobstructed adaptive dispersion to different fiber yarn, thereby avoiding the above problems.

[0050] Thus, the key technical means of the present application is not only to ply a plurality of fibers, but also to cooperate with twisting and plying.

[0051] In some embodiments, the carbon nanotube raw fiber is made by floating vapor deposition method, and is not limited thereto. Of course, this is a very efficient and low-cost raw fiber preparation method, and raw fibers made by other existing methods such as liquid phase spinning method and array spinning method can also be used.

[0052] In some embodiments, the carbon nanotube raw fiber is in a wet state of adsorbing liquid.

[0053] In some embodiments, the drawing enhancement method can further include: after the twisting treatment, performing a drying treatment to make the twisted carbon nanotube raw fiber into a fixed shape, to obtain the carbon nanotube fiber.

[0054] In some embodiments, the temperature of the drying treatment is 60-190°C, and the time is 3-10min.

[0055] In some embodiments, the number of plying of the fiber bundle is 20-200.

[0056] In some embodiments, the drawing rate of the protonated drawing is 0.5-2m / min.

[0057] In some embodiments, the protonating agent is selected from strong acid reagents.

[0058] In some embodiments, the protonating agent includes any one or a combination of the other two of chlorosulfonic acid, methyl sulfonic acid.

[0059] In some embodiments, the coagulation bath reagent includes any one or a combination of the other two of acetone, dichloromethane.

[0060] It is to be noted that the main technical means of the exemplary drawing enhancement method of the present application is to use twisting and plying to ultimately improve the mechanical strength, consistency and continuity. The specific protonation drawing and coagulation bath treatment has been fully demonstrated by the prior art, and is not limited to the selection of the above specific protonation reagent and coagulation bath reagent. Any chemical reagent that can achieve the same protonation function and coagulation function can be used.

[0061] As some typical application examples of the above technical solutions, a complete specific drawing process includes the following steps, for example:

[0062] 1) First, the original carbon nanotube fiber is twisted, and the original fiber is a wet fiber obtained by growing by the floating catalytic method and densifying by water.

[0063] 2) The twisted carbon nanotube original wet fiber obtained in step (1) is dried to more effectively maintain its twisted state and fix the twist angle.

[0064] 3) The twisted carbon nanotube fiber obtained in step (2) is plied, and then the plied fiber is continuously drawn, which includes three stages of drawing, coagulation bath cleaning and annealing:

[0065] a. In the drawing stage, the inter-fiber gaps in the plied fiber are filled and the effective contact between the fibers is increased due to the self-adaptive effect of the fiber edge shape when drawing in strong acid by plying. During the drawing process, the drawing stress can be shared by the fibers, so that the drawing force is more uniformly applied to each fiber, which is the key to achieving a higher draw ratio.

[0066] b. After the plied fiber is drawn into the coagulation bath for deprotonation cleaning, the fibers in the plied fiber have the characteristic of radial shrinkage due to the twisting treatment, and gradually shrink radially from the expanded state, and finally each filament is independent.

[0067] c. After the above drawing and cleaning, the plied fiber enters the annealing furnace for protective atmosphere annealing to further remove the residual solution in the fiber. After the above three-stage treatment, the fibers in the plied fiber are independent and can be separated.

[0068] Some specific technical parameters of the above steps are as follows:

[0069] Step (1) includes twisting the original fiber, and the twist angle is between 5-35°.

[0070] Step (2) includes drying the twisted fiber, and the drying temperature is between 60-190°C, and the drying time is 3-10 min.

[0071] Step (3) comprises: a. plying the twisted fibers, the number of fibers after plying: 20-200. The plying fibers are drawn in strong acid (chlorosulfonic acid, methyl sulfonic acid or a mixture of the two); the draw ratio is 15%-40%, and the draw rate is 0.5-2 m / min. The coagulation bath uses a solution of acetone, dichloromethane or a mixture of the two in any ratio; b. annealing the fibers obtained in step (3) under an argon environment, wherein the annealing temperature is 350-550°C, and the annealing time is 4-20 min.

[0072] The above is some specific details about fiber drawing, and the present application further provides further technical means, such as in some embodiments, the fiber bundle has a second twist angle.

[0073] The second twist angle is 2-10°.

[0074] In some embodiments, the second twist angle is less than 1 / 2 of the first twist angle.

[0075] In the present application, the plying can be direct parallel plying, that is, the multiple fiber bundles are combined into one bundle and directly used, or a certain second twist angle can be applied to the plying fiber bundle. As a further optimization of the above technical solution, the present inventors have found that applying a second twist degree can produce even more excellent technical effects, especially in the consistency of the drawn fibers.

[0076] After applying the second twist angle, during protonation expansion, the second twist degree can bring a certain inward shrinking force to the entire fiber bundle, inhibit the mutual dispersion of the fiber filaments, and produce a squeezing and bundling effect, so that the distribution state of the drawing stress becomes more uniform on the basis of the above method, thereby improving the consistency.

[0077] As for the specific twist angle setting, during drawing, due to the loosening effect of the protonation reagent, there is a certain untwisting trend of the filament bundle, and this trend acts on both the first twist angle and the second twist angle. Therefore, the second twist angle needs to be set to be significantly smaller than the first twist angle, so as to prevent the significant untwisting of the first twist angle from occurring earlier than the second twist angle, and to avoid the significant bonding between the fiber filaments due to the shrinking pressure of the second twist angle after the untwisting of a single fiber. Thus, the present inventors have continuously summarized and analyzed to propose the above quantitative relationship between the first twist angle and the second twist angle.

[0078] In some embodiments, the drawing enhancement method can specifically comprise:

[0079] annealing the precursor fiber to remove the protonated agent and / or coagulation bath agent, to obtain a reinforced fiber bundle.

[0080] In some embodiments, the drawing-reinforcing method can further include: splitting the reinforced fiber bundle to obtain a plurality of carbon nanotube reinforced fibers separated from each other.

[0081] In some embodiments, the annealing treatment is performed at a temperature of 350-550℃ for 4-20min.

[0082] Of course, the technical parameters of the above examples are only the best parameters corresponding to the limited agents currently taken by the inventors, and corresponding annealing treatment temperature and time can be appropriately adjusted to match different agents when other protonated agents and / or coagulation baths are replaced by other agents.

[0083] Moreover, the way of removing the above-mentioned protonated agent and / or coagulation bath agent is not limited to high-temperature annealing treatment, and other methods of replacing with a low-boiling-point solvent and then drying to remove the low-boiling-point solvent can also achieve the same technical effect, and any technical means that can remove the adsorbed agent from the fiber can be applied to the present application.

[0084] In some embodiments, the CV value of the tensile strength of the plurality of fibers in the obtained carbon nanotube reinforced fiber is below 5%.

[0085] In some embodiments, the continuity of the obtained carbon nanotube reinforced fiber is above 500m.

[0086] The most important technical effect of the present application is the mechanical strength, consistency and continuity of the fiber, and additionally, since the present application is a process for processing the carbon nanotube fiber after plying, the processing efficiency of the fiber is improved by tens to hundreds of times compared to the single fiber. The core point of the present application is to use the twisted fiber for plying processing, and during the coagulation bath cleaning stage after the drawing of the plying fiber, the twisted fiber has the characteristic of shrinking along its radial direction due to the deprotonation of the coagulation bath, and then the contact between the fibers is reduced, and each fiber is independent of each other, forming a separable reinforced carbon nanotube fiber. That is, using the twisted fiber for plying processing can realize batch plying processing and the characteristic of independent and separable fibers after processing. Moreover, the improvement of the processing efficiency is not only the improvement of the batch processing quantity, but more importantly, the frequency of fiber breakage is reduced, and there is no need to frequently check whether the fiber is broken and to perform the splicing operation after the breakage, which also significantly saves the production time.

[0087] Corresponding to the above-mentioned drawing-reinforcing method, the second aspect of the embodiments of the present application further provides a drawing-reinforcing system for carbon nanotube fiber, which comprises:

[0088] A plying module is used to ply the carbon nanotube fiber to obtain a fiber bundle, and the carbon nanotube fiber is in a twisted state.

[0089] A drawing module is used to protonate and draw the fiber bundle and treat the fiber bundle in a coagulation bath to obtain a precursor fiber.

[0090] A post-processing module is used to remove the protonating agent and / or the coagulation bath agent in the precursor fiber to obtain a carbon nanotube reinforced fiber.

[0091] In some embodiments, the drawing reinforcement system can further include a twisting module used to twist the carbon nanotube raw fiber to obtain the carbon nanotube fiber.

[0092] The technical solutions of the present application are further described in detail below by means of several embodiments in combination with the accompanying drawings. However, the selected embodiments are only used to illustrate the present application, and do not limit the scope of the present application.

[0093] Embodiment 1

[0094] This embodiment illustrates a process of carbon nanotube drawing reinforcement, and the process is specifically shown as follows:

[0095] Step (1): The raw fiber is twisted, and the twist angle is 10°. After twisting, the diameter of the fiber is 20 μm.

[0096] Step (2): The twisted fiber is dried, the drying temperature is 200 °C, and the drying time is 1 min.

[0097] Step (3):

[0098] a. The twisted fiber is plied, and the number of fibers after plying is 50.

[0099] b. The plied fiber is drawn in a strong acid (chlorosulfonic acid) and then passed through a coagulation bath, the drawing rate is 25%, and the drawing speed is 0.5 m / min. The coagulation bath uses acetone.

[0100] c. The fiber obtained in step (3) is annealed at a high temperature in an argon environment, the annealing temperature is 350 °C, and the annealing time is 1 min.

[0101] The final reinforced fiber is obtained in a bundle, and the continuity thereof is almost not broken, and is only limited by the maximum length of each fiber bundle. Usually, one fiber bundle can reach hundreds of meters to kilometers during processing, but it is not limited thereto. When the laboratory is transferred to actual production, larger equipment should have a higher single fiber length. The reinforced fiber can be peeled into individual fibers, and the peeled fibers are tested for surface morphology and mechanical properties, and the test results are shown in Table 1. Figures 4-5 ​

[0102] Comparative Example 1

[0103] This comparative example illustrates a process of carbon nanotube fiber drawing enhancement treatment without twisting, which is as follows:

[0104] Steps 1-2 in Example 1 are omitted, and instead the single raw fiber is directly dried and then subjected to drawing treatment under the same conditions (reagents and drawing parameters, etc.).

[0105] The surface morphology of the obtained enhanced fiber is shown in Figure 3 and the mechanical property test is shown in Figure 5 .

[0106] Comparing Figure 3 and Figure 4 It can be seen that the fiber subjected to twisting and drawing after plying has a more compact microstructure than the fiber subjected to drawing directly from the raw fiber, and multiple bundles are formed therein, which is the reason for its higher mechanical strength.

[0107] From the results in Figure 5 , it can be seen that the mechanical strength and strength consistency of the fiber obtained in Example 1 are also significantly better than those of Comparative Example 1, and after statistical analysis, the fiber strength obtained in Example 1 is 5.5 GPa, and the strength CV value is 4.5%.

[0108] In addition, the continuity of the enhanced fiber treated in this comparative example is usually between 100-600 m, and the breakage frequency is significantly higher than that of Example 1.

[0109] Comparative Example 2

[0110] This comparative example illustrates a process of carbon nanotube fiber drawing enhancement treatment, which is generally similar to Example 1, with the main difference being:

[0111] The carbon nanotube raw fiber is not twisted, but is directly dried and plying, and the plying fiber is subjected to drawing treatment and annealing treatment under the same conditions.

[0112] Since this comparative example lacks the step of twisting treatment, the adhesion between the fibers due to plying is very serious, and a part of the fibers cannot be separated from the fiber bundle.

[0113] In addition, the mechanical strength and consistency of the fiber are also significantly worse than those of Example 1, the mechanical strength is slightly lower than that of Comparative Example 1, and the strength CV value is as high as 8%.

[0114] In addition, the continuity of the enhanced fiber treated in this comparative example is usually between 200-300 m.

[0115] Comparative Example 3

[0116] This comparative example illustrates a process of carbon nanotube fiber drawing enhancement treatment, which is generally similar to that of Example 1, with the main difference being that:

[0117] After the carbon nanotube raw fiber is twisted and dried, it is not cabled, but is subjected to drawing treatment and annealing treatment under the same conditions as the twisted single fiber.

[0118] The mechanical strength and consistency of the obtained fiber are also significantly poorer than those of Example 1, and since the twisted single fiber is directly drawn, it can cause local stress concentration inside the fiber, and since this stress concentration is not dispersed by the multiple fibers in the cabling, the average mechanical strength of the obtained fiber can even be significantly lower than that of Comparative Example 1 (about 30% reduction), and the strength CV value is as high as 15%.

[0119] In addition, the continuity of the reinforced fiber treated in this comparative example is generally between 10-50m.

[0120] Example 2

[0121] This example illustrates a process of carbon nanotube drawing enhancement treatment, which is generally similar to that of Example 1, with the main difference being that:

[0122] After cabling the fiber, a second light twist is applied to the fiber bundle, so that the fiber bundle has a second twist angle of 5°.

[0123] The strength of the fiber obtained in this example is at the same level as that of Example 1, but the consistency is better, with the strength CV value reduced to 3.5%.

[0124] Comparative Example 4

[0125] This comparative example is generally similar to Example 2, with the main difference being that:

[0126] The second twist angle applied is the same as the angle of the first twist applied to the raw fiber.

[0127] This comparative example is somewhat similar to Comparative Example 2, and since the degree of the second twist is too high, it causes strong inward extrusion force of the fiber bundle, thus causing a little adhesion between the fibers, affecting the consistency, and the strength CV value is significantly increased to 9.0%.

[0128] Example 3

[0129] This example illustrates the effect of the twist angle of the raw fiber on the mechanical properties, as shown below:

[0130] The twist angle of the raw fiber is changed, and the initial mechanical properties of the raw carbon nanotube with different twist angles are tested as shown in Figure 2a The fiber morphology is as shown in Figure 2bThe drawing and post-treatment were carried out under the same conditions, and the related mechanical properties were tested.

[0131] The results show that different twisting angles have an impact on the mechanical properties, but the final obtained fibers are better than those without twisting (0°).

[0132] Example 4

[0133] This example is generally similar to Example 1, the main difference being that:

[0134] The annealing temperature adopts a gradient temperature, that is, four temperature zones are used for annealing from the position where the fiber enters the annealing furnace, with a degree gradient of 150-200-300-350℃. The final obtained fiber mechanical strength is similar to that of Example 1, but the CV value is further reduced to 3%. And due to the use of gradient temperature, the fiber static annealing state is more moderate, and the fiber processing speed is improved (0.8 m / min), avoiding the irregular phenomenon of the fiber directly entering the high temperature zone for annealing.

[0135] Therefore, it can be determined that, on the basis of the above technical solutions provided by the present application, further using a gradient heating method during annealing can further optimize the consistency of the fiber.

[0136] Example 5

[0137] This example is generally similar to Example 1, the main difference being that:

[0138] The number of plies is changed, respectively 20 and 200, and the mechanical strength, consistency and continuity of the finally obtained fiber are basically unchanged compared with Example 1.

[0139] Based on the above examples and comparative examples, it can be clear that the drawing and strengthening method provided by the example of the present application twists and plies the carbon nanotube fiber, and performs strong acid assisted drawing on the plied fiber bundle. After the fiber bundle is protonated and expanded by strong acid, the self-adaptive effect is generated on the edge shape of each expanded fiber in the fiber bundle, the gap between the plied fibers is filled, and the effective contact between the fibers is increased. During the drawing process, the effective contact between the fibers can transmit the drawing stress to each other, so that the stress is more uniformly applied to each fiber, thereby greatly improving the stability of the fiber during the drawing process, so as to realize a higher drawing rate and drawing rate, and finally significantly improve the mechanical strength and consistency of the strengthened fiber, and bring very excellent continuity, which is very beneficial to the application of carbon nanotube fiber.

[0140] In addition, the method provided by the example of the present application also brings a very significant preparation efficiency advantage, which is not only the improvement of the batch processing quantity brought by the drawing of multiple fibers together, but also the continuity brought by the extremely high continuity.

[0141] It should be understood that the above-described embodiments are merely exemplary of the technique concept and characteristics of the present application, and are intended to give a person skilled in the art a comprehensive understanding of the present application and to enable him to implement the present application, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and principle of the present application shall be covered within the protection scope of the present application.

Claims

1. A method of drawing enhancement of carbon nanotube fibers, characterized by, The application relates to a carbon nanotube fiber, a fiber bundle, a precursor fiber and a reinforced fiber bundle. The carbon nanotube fiber is obtained by twisting treatment of a carbon nanotube raw fiber, the carbon nanotube raw fiber is prepared by a floating vapor deposition method, the first twisting angle of the carbon nanotube fiber is 5-35 DEG, and the diameter of the carbon nanotube fiber is 10-50 mu m. The carbon nanotube fiber is subjected to pitting treatment to obtain a fiber bundle, the pitting number of the fiber bundle is 20-200, and the fiber bundle has a second twisting angle which is less than 1 / 2 of the first twisting angle. The fiber bundle is subjected to protonation stretching and coagulation bath treatment to obtain a precursor fiber, wherein, after the fiber bundle is expanded by strong acid protonation, the edge shape of each expanded fiber in the fiber bundle is self-adapted, the inter-fiber gap is filled, the effective contact area between the fibers is increased, and the stretching stress is transmitted between the fibers during the stretching process, so that the stress is uniformly applied to each fiber. The precursor fiber is subjected to annealing treatment to remove the protonation reagent and / or the coagulation bath reagent to obtain a reinforced fiber bundle. The reinforced fiber bundle is disassembled to obtain a plurality of carbon nanotube reinforced fibers which are separated from each other.

2. Drafting enhancement method according to claim 1, characterized in that, The carbon nanotube raw fiber is in a wet state of adsorbing liquid, and is subjected to drying treatment after the twisting treatment to shape the carbon nanotube raw fiber after the twisting treatment, to obtain the carbon nanotube fiber, wherein the temperature of the drying treatment is 60-190 DEG C, and the time is 3-10 min.

3. The draft enhancement method of claim 1 wherein, The stretching rate of the protonation stretching is 0.5-2 m / min.

4. The draft enhancement method of claim 3, wherein, The protonation reagent is selected from strong acid reagents.

5. The draft enhancement method according to claim 4, characterized in that, The protonation reagent includes any one or a combination of chlorosulfonic acid and methyl sulfonic acid.

6. The draft enhancement method of claim 1 wherein, The coagulation bath reagent includes any one or a combination of acetone and dichloromethane.

7. The draft enhancement method of claim 1 wherein, The temperature of the annealing treatment is 350-550 DEG C, and the time is 4-20 min.

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