Densified carbon tube / polyurea composite fiber as well as preparation method and application thereof

Abstract

The invention provides a densified carbon tube / polyurea composite fiber and a preparation method and application thereof, the preparation method comprises the following steps: an acidified carbon tube is divided into two parts, one part of the carbon tube is pre-dispersed in N-N dimethylformamide, then polyurea and the other part of the carbon tube are added, and a spinning solution is obtained; carrying out wet spinning and coagulating bath forming on the spinning solution to obtain nascent fibers with holes; suspending and drying the nascent fiber to obtain a densified carbon tube / polyurea composite fiber, and applying the carbon tube / polyurea composite fiber to artificial muscle. The densified carbon tube / polyurea composite fiber is prepared through pre-dispersion of part of the carbon tubes, wet spinning and suspension drying and has high strength, high electric heating performance, high thermal actuating stress and high electric actuating stress, and the output performance of the carbon tube / polyurea composite fiber is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of nanocomposite materials technology, and in particular to a densified carbon nanotube / polyurea composite fiber, its preparation method, and its application. Background Technology

[0002] Artificial muscles, or actuators, are novel intelligent polymer materials capable of generating reversible, specific movement patterns in response to external stimuli (such as temperature, humidity, electricity, and light). These movement patterns typically include bending, twisting, and contraction. With the continuous development of soft robotics and wearable electronic devices, the demand for high-performance artificial muscles is becoming increasingly urgent. These materials not only need to meet the requirements of different actuation modes but also stable high-output performance to adapt to various application scenarios. Traditional shape memory polymer materials are limited by their poor mechanical properties, slow response, and inefficient stress output, making them unsuitable for the needs of novel artificial muscles.

[0003] In the current context, combining shape memory polymers with carbon-based materials (carbon nanotubes, graphene, carbon black, etc.) is leading a new trend in the field of artificial muscles. Artificial muscles can be driven by specific stimuli, and composite materials containing various fillers can simultaneously achieve multiple driving modes, widely regarded as a replacement for traditional shape memory polymers. However, the requirements for superior artificial muscles go beyond multiple driving modes; they also include multiple standards such as mechanical strength, flexibility, response speed, and output performance to adapt to the modern application scenarios of new artificial muscles. Furthermore, artificial muscles can replace human muscles to perform some labor, especially in extreme, complex, and special situations; therefore, the importance of high-output and stable artificial muscles is self-evident.

[0004] In summary, high-performance artificial muscle materials have become a key driving force in the evolution of soft robots, while shape memory composites with excellent carbon-based fillers have become a highly sought-after material choice to meet the modern needs of novel artificial muscles. Summary of the Invention

[0005] This invention proposes a densified carbon nanotube / polyurea composite fiber, its preparation method, and its application. The densified carbon nanotube / polyurea composite fiber is prepared by pre-dispersing carbon nanotubes, wet spinning, and hanging drying. It has high strength, high electrothermal properties, high thermal actuation stress, and high electro actuation stress, which significantly improves its output performance.

[0006] The technical solution of this invention is achieved as follows: a method for preparing densified carbon nanotube / polyurea composite fibers, comprising the following steps:

[0007] (1) The acidified carbon nanotubes (carbon nanotubes, MCNTs) are divided into two parts. One part of the carbon nanotubes is pre-dispersed in N-N dimethylformamide, and then polyurea and the other part of the carbon nanotubes are added and mixed to obtain the spinning solution.

[0008] (2) The spinning solution is subjected to wet spinning and coagulation bath molding to obtain nascent fibers with pores.

[0009] (3) The nascent fibers are hung and dried to obtain densified carbon nanotube / polyurea composite fibers.

[0010] In step (1), by pre-dispersing some carbon nanotubes, these carbon nanotubes can be uniformly and stably dispersed in the solution, which can enhance the mechanical properties of the fiber. In addition, the stably dispersed carbon nanotubes can form a complete conductive network inside the fiber, thereby improving the electrical properties of the composite fiber.

[0011] In step (3), the polyurea melts and shrinks at high temperature, and the pores generated by the solution exchange in the coagulation bath of the nascent fibers continuously shrink until they disappear, forming a dense composite fiber. Furthermore, the carbon nanotubes and polymer chains are tightly bonded together, generating strong interactions that further enhance the fiber. Compared to other drying methods, hanging drying can maintain the cylindrical shape of the fiber.

[0012] Furthermore, in step (1), the concentration of pre-dispersed carbon nanotubes in NN dimethylformamide is 0.3-3 mg / mL, which can be 0.3 mg / mL, 0.33 mg / mL, 1 mg / mL, 2.67 mg / mL, 3 mg / mL, etc.; the pre-dispersed carbon nanotubes account for 1.25 wt%-12.5 wt% of the total carbon nanotubes, which can be 1.25 wt%, 4 wt%, 11 wt%, 12.5 wt%, etc.

[0013] Furthermore, in step (2), the coagulation bath is deionized water.

[0014] Furthermore, in step (3), the carbon nanotube / polyurea composite fiber contains 1-30 wt% carbon nanotubes, which can be 1 wt%, 1.1 wt%, 7.5 wt%, 11.9 wt%, 16.6 wt%, 20 wt%, 27 wt%, 30 wt%, etc.

[0015] Furthermore, in step (3), the hanging drying temperature is 70-140℃ and the drying time is 5-6h.

[0016] A densified carbon nanotube / polyurea composite fiber is prepared using the preparation method described above.

[0017] Application of a densified carbon nanotube / polyurea composite fiber in artificial muscle.

[0018] Furthermore, the artificial muscle is thermally driven and / or electrically driven.

[0019] The beneficial effects of this invention are:

[0020] This invention employs a pre-dispersion method to enhance the mechanical and electrical properties of composite fibers. Furthermore, a high-temperature heat-assisted suspension drying method is used to continuously fuse and eventually eliminate the pores within the fibers, resulting in a strong interaction between carbon nanotubes and polymers (van der Waals forces, hydrogen bonds, π-π interactions, etc.), significantly improving the mechanical and electrical properties of the composite fibers. The carbon nanotube / polyurea composite fibers prepared by this invention through pre-dispersion of carbon nanotubes, wet spinning, and suspension drying for densification exhibit high strength (reaching 109 MPa), high electrothermal performance (Joule heat energy reaching 75°C), high thermal actuation stress (reaching 28 MPa), and high electrodynamic stress (reaching 22 MPa). Higher mechanical properties of the composite fiber allow for greater energy storage and release during shape memory, significantly improving its output performance. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The images are electron microscope images of fiber cross sections. (a) shows nascent fibers, and (b) shows densified carbon nanotube / polyurea composite fibers.

[0023] Figure 2 The thermal / electro-induced stress curves of carbon nanotube / polyurea composite fibers and the thermal-induced stress of pure polymer fibers (PU);

[0024] Figure 3 The electrical conductivity of the carbon nanotube / polyurea composite fibers prepared in Example 5 and Comparative Example 3;

[0025] Figure 4 This is a photograph of the pre-dispersed carbon nanotube solution after it has been inverted. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In this embodiment of the invention, the acidified carbon nanotubes were obtained by soaking carbon nanotubes in nitric acid solution at 120°C for 12 hours.

[0028] Polyurea was prepared using the method described on page 4 of the literature "Christopher B. Cooper et al., High Energy Density Shape Memory Polymers Using Strain-Induced Supramolecular Nanostructures, ACS Cent. Sci. 2021, 7, 1657-1667".

[0029] Polyurea and acidified carbon nanotubes can also be prepared by other methods or purchased commercially.

[0030] Example 1

[0031] A method for preparing densified carbon nanotube / polyurea composite fibers includes the following steps:

[0032] (1) 0.12g of acidified carbon nanotubes were divided into two parts. One part of the carbon nanotubes was ultrasonically pre-dispersed in 5mL of N,N dimethylformamide. The concentration of the pre-dispersed carbon nanotubes was 3mg / mL. The pre-dispersed carbon nanotubes accounted for 12.5wt% of the total carbon nanotubes. Pre-dispersion improved the dispersibility of carbon nanotubes and improved the electrical properties of the composite fiber. Then, 0.6g of polyurea and the other part of carbon nanotubes were added and mixed to obtain the spinning solution.

[0033] Figure 4 This is a photograph of the pre-dispersed carbon nanotube solution after it has been inverted. From Figure 4 As can be seen, agglomeration occurs when the carbon nanotube concentration is greater than 3 mg / mL. Therefore, in this embodiment, a pre-dispersed carbon nanotube concentration of 3 mg / mL is used.

[0034] (2) The spinning solution is wet-spun and extruded through a 21G needle at a speed of 10 ml / h. Then it is formed in a coagulation bath (deionized water) to obtain nascent fibers with pores.

[0035] (3) The nascent fibers were suspended and dried in a drying oven at 120°C for 5 hours. This process removed the pores left inside the fibers due to solution exchange, thereby increasing the fiber density and obtaining densified carbon nanotube / polyurea composite fibers. The carbon nanotube content in the carbon nanotube / polyurea composite fibers was 16.6%.

[0036] After the treatment in step (3), the fiber density decreased from 0.18 g / cm³. 3 Increased to 1.43 g / cm³ 3 The nascent fibers are dried by hanging, which increases the contact between carbon nanotubes and between carbon nanotubes and polymer chains, resulting in strong interactions and thus improving the mechanical and output properties of the composite fibers.

[0037] The cross-section of the carbon nanotube / polyurea composite fiber prepared in Example 1 was tested using a scanning electron microscope, as shown below. Figure 1 As shown, the nascent fibers contain pores, while the carbon nanotube / polyurea composite fibers have no pores and are more dense. The actuation stress was tested using a tensile testing machine. Figure 2 As shown, the thermal / electric actuation stress of the composite fiber is 28 / 22 MPa. The prepared carbon nanotube / polyurea composite fiber can be used in artificial muscles, driven by thermal and / or electric actuation.

[0038] A carbon nanotube / polyurea composite fiber with a carbon nanotube content of 16.6 wt%, a length of 15 mm, and a diameter of 180 μm was taken from Example 1 above. Both ends were fixed to the fixed and movable clamps of a stretching machine, respectively, with 15 mm of the carbon nanotube / polyurea composite fiber exposed between the clamps. The stretching speed was 15 mm / min until a specific pre-strain value of 60% was reached. Then, external thermal stimulation (hot air blower) was applied. The carbon nanotube / polyurea composite fiber, due to heat, tended to contract, generating thermal kinetic energy. The stretching machine simultaneously recorded the elongation and the resulting actuation stress of the carbon nanotube / polyurea composite fiber. The highest measured thermal actuation stress of the carbon nanotube / polyurea composite fiber was 28 MPa. Using the same method, after replacing the external stimulation with electrical stimulation, the highest measured electrical actuation stress of the fiber was 22 MPa.

[0039] Mechanical and electrical tests were conducted on a 15 mm long and 180 μm diameter carbon nanotube / polyurea composite fiber prepared in Example 1. The composite fiber contained 16.6 wt% carbon nanotubes, had a breaking stress of 109 MPa, and an electrical conductivity of 17 S / m.

[0040] Example 1: A composite fiber of carbon nanotube and polyurea with a length of 20 mm and a diameter of 180 μm was cut from Example 1 above. Electrodes were connected to both ends. A KEITHLEY2400 was used to provide power. The Joule heat generated under a current of 3 mA reached 75°C.

[0041] Example 2

[0042] This embodiment is basically the same as Embodiment 1, except that the content of carbon nanotubes in the carbon nanotube / polyurea composite fiber is 11.9 wt%.

[0043] Example 3

[0044] This embodiment is basically the same as Embodiment 1, except that the content of carbon nanotubes in the carbon nanotube / polyurea composite fiber is 7.5 wt%.

[0045] Example 4

[0046] This embodiment is basically the same as Embodiment 1, except that the content of carbon nanotubes in the carbon nanotube / polyurea composite fiber is 1.1 wt%.

[0047] Example 5

[0048] This embodiment is basically the same as Embodiment 1, except that the content of carbon nanotubes in the carbon nanotube / polyurea composite fiber is 20wt%.

[0049] Comparative Example 1

[0050] This embodiment is basically the same as embodiment 1, except that: in step (1), carbon nanotubes are not added, and the process proceeds directly to step (2), where the fiber is placed in a drying oven for suspended drying. The resulting pure polymer fiber (PU) has poor mechanical strength, and the measured thermal actuation stress is 8 MPa, indicating poor actuation performance.

[0051] Comparative Example 2

[0052] This embodiment is basically the same as embodiment 1, except that step (3) is omitted and the tensile strength of the nascent fiber is measured to be 10 MPa. Since the strength of the fiber itself is low, the actuation stress cannot be measured.

[0053] Comparative Example 3

[0054] This embodiment is basically the same as Embodiment 5, except that in step (1), it is not necessary to divide the acidified carbon nanotubes into two parts or to perform partial pre-dispersion of the carbon nanotubes. Instead, the polyurea and carbon nanotubes are directly dispersed in N,N-dimethylformamide and mixed to obtain a spinning solution. A carbon nanotube / polyurea composite fiber with a carbon nanotube content of 27.42 wt% is prepared.

[0055] exist Figure 3 In the examples, the carbon nanotube content of 27.42 wt% corresponds to the carbon nanotube / polyurea composite fiber prepared in Comparative Example 3, and the carbon nanotube content of 20% corresponds to the carbon nanotube / polyurea composite fiber prepared in Example 5. Figure 3 It can be seen that carbon nanotube / polyurea composite fibers prepared by pre-dispersing carbon nanotubes have high electrical conductivity even when the carbon nanotube content is only 20%.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a densified carbon nanotube / polyurea composite fiber, characterized in that, Includes the following steps: (1) The acidified carbon nanotubes are divided into two parts. One part of the carbon nanotubes is pre-dispersed in N,N dimethylformamide, and then polyurea and the other part of the carbon nanotubes are added and mixed to obtain the spinning solution. (2) The spinning solution is subjected to wet spinning and coagulation bath molding to obtain nascent fibers with pores. (3) The nascent fibers are hung and dried to obtain densified carbon nanotube / polyurea composite fibers.

2. The method for preparing a densified carbon nanotube / polyurea composite fiber according to claim 1, characterized in that, In step (1), the concentration of pre-dispersed carbon nanotubes in NN dimethylformamide is 0.3-3 mg / mL, and the pre-dispersed carbon nanotubes account for 1.25 wt%-12.5 wt% of the total carbon nanotubes.

3. The method for preparing a densified carbon nanotube / polyurea composite fiber according to claim 1, characterized in that, In step (2), the coagulation bath is deionized water.

4. The method for preparing a densified carbon nanotube / polyurea composite fiber according to claim 1, characterized in that, In step (3), the carbon nanotube content in the carbon nanotube / polyurea composite fiber is 1-30 wt%.

5. The method for preparing a densified carbon nanotube / polyurea composite fiber according to claim 1, characterized in that, In step (3), the temperature for hanging drying is 70-140℃ and the drying time is 5-6h.

6. A densified carbon nanotube / polyurea composite fiber, prepared by the preparation method according to any one of claims 1-5.

7. The application of the densified carbon nanotube / polyurea composite fiber as described in claim 6 in artificial muscle.

8. The application according to claim 7, characterized in that, The artificial muscle is thermally and / or electrically driven.

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