In-situ hydrogen-bond enhanced aramid nanofiber / carbon nanotube composite fiber and preparation method thereof

Abstract

The application belongs to the field of composite materials, and particularly relates to an in-situ hydrogen bond reinforced aramid nanofiber / carbon nanotube composite fiber and a preparation method thereof. The application first performs hydrophilic treatment on a carbon nanotube fiber, then places the treated carbon nanotube fiber in an aramid nanofiber solution for infiltration, places the carbon nanotube fiber in a proton donor coagulation bath for infiltration, finally places the carbon nanotube fiber in a shrinkage solvent for infiltration, and dries to obtain the in-situ hydrogen bond reinforced aramid nanofiber / carbon nanotube composite fiber. By introducing a hydrogen bond into a nanochannel of the carbon nanotube, the mechanical property of the carbon nanotube fiber is effectively improved, and the application scenario of the carbon nanotube fiber can be widened.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to an in-situ hydrogen bond-reinforced aramid nanofiber / carbon nanotube composite fiber and its preparation method. Background Technology

[0002] Carbon nanotubes possess a unique atomic and electronic structure, along with excellent mechanical properties, thermal conductivity, and electrical conductivity. However, because carbon nanotube fibers are constructed from carbon nanotubes through relatively weak van der Waals forces and are loosely assembled, the contact area between the carbon nanotubes is very small. Consequently, the tensile strength of carbon nanotube fibers is much lower than that of a single carbon nanotube. To improve the tensile strength of carbon nanotube fibers, it is essential to enhance the interaction forces between the carbon nanotubes.

[0003] Several strategies exist to enhance the interactions between carbon nanotubes, such as solvent densification of carbon nanotube fibers to make them more tightly assembled (Nat. Commun. 2019, 10, 2962), or polymer infiltration of carbon nanotube fibers (ACS Nano 2010, 4, 5827). However, these two methods only reduce the distance between carbon nanotubes or fill the gaps between them, which are physical enhancements without introducing stronger forces, such as chemical bonds, to strengthen the tensile strength of the fibers. Building on this, some researchers have introduced carbon-carbon covalent bonds between carbon nanotubes (Carbon 2019, 146, 627). This method can significantly increase the interaction forces between carbon nanotube fibers, but the experimental conditions are harsh, and the flexibility of the carbon nanotube fibers is severely reduced, affecting their performance. To achieve continuous in-situ reinforcement of carbon nanotube fibers, it is necessary to simplify experimental conditions while conveniently introducing strong intermolecular forces.

[0004] Compared to covalent bonds, which have higher requirements for formation, hydrogen bonds, with their moderate strength and ease of formation, have attracted widespread attention. The strength of a hydrogen bond ranges from 4.2 to 167.4 kJ / mol, stronger than the strength of van der Waals forces (0.4-4 kJ / mol). If hydrogen bonds can be introduced into carbon nanotube fibers, in-situ hydrogen bond reinforcement can be achieved, improving the mechanical strength of the carbon nanotube fibers and thus broadening their application scenarios. Summary of the Invention

[0005] The purpose of this invention is to address the problems of insufficient tensile strength of carbon nanotube fibers prepared by existing processes, which limits their further applications, by providing an in-situ hydrogen-bonded reinforced aramid nanofiber / carbon nanotube composite fiber and its preparation method, aiming to improve the mechanical properties of carbon nanotube fibers.

[0006] The method for preparing in-situ hydrogen-bonded reinforced aramid nanofiber / carbon nanotube composite fibers provided by this invention comprises the following steps:

[0007] (1) First, the carbon nanotube fibers are subjected to hydrophilic treatment, and then they are immersed in an aramid nanofiber solution to fill the nanopores of the carbon nanotubes with aramid nanofibers; the solid content of the aramid nanofiber solution is 0.005wt%-1wt%.

[0008] (2) Then, the carbon nanotube fibers will be immersed in a proton donor coagulation bath and form hydrogen bonds with the functional groups on the surface of the carbon nanotube fibers; wherein the proton donor coagulation bath is one or more of deionized water, methanol, ethanol, acetone, ethylene glycol, inorganic acid and organic acid.

[0009] (3) Finally, the fiber is immersed in a shrinking solvent and dried to obtain an in-situ hydrogen bond-reinforced aramid nanofiber / carbon nanotube composite fiber; wherein the shrinking solvent is one or more of ethanol, acetone, dichloromethane, and ethylene glycol.

[0010] This invention effectively enhances the mechanical properties of carbon nanotube fibers and broadens their application scenarios by generating hydrogen bonds in situ within the nanopores of carbon nanotubes.

[0011] In this invention:

[0012] The hydrophilic treatment is one or more of oxygen plasma treatment and acid treatment.

[0013] The solid content of the aramid nanofiber solution is preferably 0.01wt%-0.05wt%.

[0014] In this invention:

[0015] When the hydrophilic treatment method is oxygen plasma treatment, the steps are as follows: place the carbon nanotube fibers in a plasma cleaner, set the power to 100-500W, preferably 100-200W; the time is 0.5-20min, preferably 0.5-3min, and oxygen is introduced for plasma treatment.

[0016] When the hydrophilic treatment method is acid treatment, the steps are as follows: place the carbon nanotube fibers in a round-bottom flask, add a strong inorganic acid, heat under reflux, rinse thoroughly with deionized water, and then dry.

[0017] In this invention:

[0018] The strong inorganic acid is one or more of concentrated nitric acid, concentrated hydrochloric acid, and concentrated sulfuric acid.

[0019] The heating reflux time is 2-10 hours, preferably 3-6 hours.

[0020] The aramid nanofiber / carbon nanotube composite fiber prepared by this invention has excellent mechanical properties. After further twisting to a diameter of 30-100 μm, the elongation at break is 10%; its tensile strength reaches 1.23 GPa.

[0021] This invention achieves in-situ hydrogen bond enhancement of carbon nanotube fibers by introducing hydrogen bonds, effectively improving the mechanical properties of carbon nanotube fibers and broadening their application scenarios.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) Compared with pure carbon nanotube fibers, the in-situ hydrogen bond-enhanced aramid nanofiber / carbon nanotube composite fiber effectively improves the mechanical properties of carbon nanotube fibers due to the introduction of stronger hydrogen bonds between carbon nanotubes. It can be further macroscopically assembled into various forms, making the application of carbon nanotube fibers more extensive.

[0024] (2) The preparation process of this composite fiber is simple. It only requires hydrophilic treatment first, then immersion in aramid nanofiber solution, then immersion in proton donor coagulation bath, and finally immersion in shrinkage solvent and drying to enhance carbon nanotube fibers in situ with hydrogen bonding. It has a certain prospect for large-scale production. Attached Figure Description

[0025] Figure 1 This is a transmission electron microscope (TEM) image of aramid nanofibers.

[0026] Figure 2 The images show the morphology of carbon nanotube fibers before and after reinforcement. In the images, a represents the morphology of unreinforced carbon nanotube fibers, b is a magnified view, c represents the morphology of in-situ hydrogen-bonded aramid nanofiber / carbon nanotube composite fibers, and d is a magnified view.

[0027] Figure 3 A comparison of the mechanical properties of enhanced carbon nanotube fibers and in-situ hydrogen-bonded carbon nanotube composite fibers. Detailed Implementation

[0028] Example 1: Aramid nanofiber / carbon nanotube composite fiber (ethylene glycol shrinkage)

[0029] Step 1: Oxygen plasma treatment of carbon nanotube fibers

[0030] Carbon nanotube fibers were placed in a plasma cleaner with a power of 150W and a treatment time of 2 minutes. Oxygen was introduced for treatment to obtain oxygen plasma-treated carbon nanotube fibers.

[0031] Step 2: Preparation of aramid nanofibers by chemical pyrolysis

[0032] Take 86.8 mL (95.5 g) of dimethyl sulfoxide and one cylindrical magnetic stir bar, and add them sequentially to a beaker. Then take 0.2 g of para-aramid fibers, 0.3 g of potassium hydroxide, and 4 mL of deionized water, and add them sequentially to the aforementioned beaker. Seal the mouth of the beaker with plastic wrap and aluminum foil, and place the beaker on a magnetic stirring table. Stir at room temperature for 4 hours. Vacuum filter the resulting solution using a sintered glass funnel to obtain a mixed solution of aramid nanofibers and dimethyl sulfoxide. Store the solution in a dry, dark place to obtain aramid nanofibers.

[0033] The structure of aramid nanofibers is as follows Figure 1 As shown in the transmission electron microscope.

[0034] Step 3: Preparation of aramid nanofiber / carbon nanotube composite fibers

[0035] The mixed solution of aramid nanofibers and dimethyl sulfoxide obtained in step 2 was diluted 20 times and sonicated for 15 min. Then, the carbon nanotubes treated with oxygen plasma were immersed in the above solution for 5 min, then immersed in deionized water (as a proton donor coagulation bath) for 10 min, and finally immersed in the shrinking solvent ethylene glycol for 2 min. After drying, in-situ hydrogen bond-reinforced aramid nanofiber / carbon nanotube composite fibers were obtained.

[0036] Morphological comparison of reinforced and unreinforced fibers: Figure 2 As shown in the scanning electron microscope, after in-situ hydrogen bonding reinforcement of carbon nanotube fibers with aramid nanofibers, it can be seen that the aramid nanofibers are fully filled in the nanopores.

[0037] Tensile tests were conducted on the fiber using an electronic universal testing machine, and the average tensile strength reached 1.23 GPa, which is 92.2% higher than that of unreinforced carbon nanotube fibers, demonstrating significant improvement. Figure 3 ).

[0038] Example 2: Aramid nanofiber / carbon nanotube composite fiber (ethanol shrinkage)

[0039] Step 1: Oxygen plasma treatment of carbon nanotube fibers

[0040] Carbon nanotube fibers were placed in a plasma cleaner with a power of 150W and a treatment time of 2 minutes. Oxygen was introduced for treatment to obtain oxygen plasma-treated carbon nanotube fibers.

[0041] Step 2: Preparation of aramid nanofibers by chemical pyrolysis

[0042] Take 86.8 mL (95.5 g) of dimethyl sulfoxide and one cylindrical magnetic stir bar, and add them sequentially to a beaker. Then take 0.2 g of para-aramid fibers, 0.3 g of potassium hydroxide, and 4 mL of deionized water, and add them sequentially to the aforementioned beaker. Seal the mouth of the beaker with plastic wrap and aluminum foil, and place the beaker on a magnetic stirring table. Stir at room temperature for 4 hours. Vacuum filter the resulting solution using a sintered glass funnel to obtain a mixed solution of aramid nanofibers and dimethyl sulfoxide. Store the solution in a dry, dark place to obtain aramid nanofibers.

[0043] Step 3: Preparation of aramid nanofiber / carbon nanotube composite fibers

[0044] The mixed solution of aramid nanofibers and dimethyl sulfoxide obtained in step 2 was diluted 20 times and sonicated for 15 min. Then, the carbon nanotubes treated with oxygen plasma were immersed in the above solution for 5 min, then immersed in deionized water (as a proton donor coagulation bath) for 10 min, and finally immersed in the shrinking solvent ethanol for 2 min. After drying, in-situ hydrogen bond-reinforced aramid nanofiber / carbon nanotube composite fibers were obtained.

[0045] The fiber was subjected to tensile testing using an electronic universal testing machine, and the average tensile strength reached 711.31 MPa, which is 11.1% higher than that of unreinforced carbon nanotube fibers.

[0046] Example 3: Aramid nanofiber / carbon nanotube composite fiber (aramid nanofiber / dimethyl sulfoxide solution concentration changed)

[0047] Step 1: Oxygen plasma treatment of carbon nanotube fibers

[0048] Carbon nanotube fibers were placed in a plasma cleaner with a power of 150W and a treatment time of 2 minutes. Oxygen was introduced for treatment to obtain oxygen plasma-treated carbon nanotube fibers.

[0049] Step 2: Preparation of aramid nanofibers by chemical pyrolysis

[0050] Take 86.8 mL (95.5 g) of dimethyl sulfoxide and one cylindrical magnetic stir bar, and add them sequentially to a beaker. Then take 0.2 g of para-aramid fibers, 0.3 g of potassium hydroxide, and 4 mL of deionized water, and add them sequentially to the aforementioned beaker. Seal the mouth of the beaker with plastic wrap and aluminum foil, and place the beaker on a magnetic stirring table. Stir at room temperature for 4 hours. Vacuum filter the resulting solution using a sintered glass funnel to obtain a mixed solution of aramid nanofibers and dimethyl sulfoxide. Store the solution in a dry, dark place to obtain aramid nanofibers.

[0051] Step 3: Preparation of aramid nanofiber / carbon nanotube composite fibers

[0052] The mixed solution of aramid nanofibers and dimethyl sulfoxide obtained in step 2 was diluted 10 times and sonicated for 15 min. Then, the carbon nanotubes treated with oxygen plasma were immersed in the above solution for 5 min, then immersed in deionized water (as a proton donor coagulation bath) for 10 min, and finally immersed in the shrinking solvent ethylene glycol for 2 min. After drying, in-situ hydrogen bond-reinforced aramid nanofiber / carbon nanotube composite fibers were obtained.

[0053] The fiber was subjected to tensile testing using an electronic universal testing machine, and the average tensile strength reached 1 GPa, which is 56.9% higher than that of unreinforced carbon nanotube fibers.

Claims

1. A method for preparing in-situ hydrogen-bonded reinforced aramid nanofiber / carbon nanotube composite fibers, characterized in that, The specific steps are as follows: (1) First, the carbon nanotube fibers are subjected to hydrophilic treatment, and then they are immersed in an aramid nanofiber solution to fill the nanopores of the carbon nanotubes; wherein the solid content of the aramid nanofiber solution is 0.005 wt%-1 wt% (2) Then, the carbon nanotube fibers filled with aramid nanofibers obtained in step (1) are immersed in a proton donor coagulation bath to form hydrogen bonds with the functional groups on the surface of the carbon nanotube fibers; wherein the proton donor coagulation bath is deionized water. (3) Finally, the fiber is immersed in a shrinking solvent and dried to obtain in-situ hydrogen bond-reinforced aramid nanofiber / carbon nanotube composite fiber; wherein the shrinking solvent is one or more of ethanol, acetone, dichloromethane, and ethylene glycol. The hydrophilic treatment is one or more of oxygen plasma treatment and acid treatment; wherein the acid solution used in the acid treatment is one or more of concentrated nitric acid and concentrated sulfuric acid.

2. The preparation method according to claim 1, characterized in that: When the hydrophilic treatment method is oxygen plasma treatment, the steps are as follows: place the carbon nanotube fibers in a plasma cleaner, set the power to 100-500 W, and the time to 0.5-20 min; introduce oxygen for plasma treatment. When the hydrophilic treatment method is acid treatment, the steps are as follows: place the carbon nanotube fibers in a round-bottom flask, then add the acid solution, heat under reflux for 2-10 hours, then rinse thoroughly with deionized water and dry.

3. An in-situ hydrogen-bonded reinforced aramid nanofiber / carbon nanotube composite fiber obtained by the preparation method described in claim 1 or 2.

4. The in-situ hydrogen bond-reinforced aramid nanofiber / carbon nanotube composite fiber according to claim 3, after further twisting, has a diameter of 30-100 µm, a tensile elongation at break of 10%, and a tensile strength of 1.23 GPa.

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