A whisker-like graphene-modified aramid III composite fiber and its preparation method

Abstract

A whisker-like graphene-modified aramid III composite fiber and its preparation method are disclosed. The modified aramid III fiber comprises whisker-like sulfur-doped graphene with a length of 150 nm–20 μm and a sulfur doping content of 1 atom%–4.56 atom%. This invention uses whisker-like sulfur-doped graphene as a reinforcement for the aramid III fiber. Through in-situ polymerization, the whisker-like structure of the graphene is used to induce further crystallization and orientation of the aramid III. Simultaneously, the doped sulfur element enhances the dispersibility of graphene in DMAC solvent and forms hydrogen bonds with aramid III molecules. This not only strengthens the intermolecular forces of the aramid III molecular chains but also densifies the fibers, thereby comprehensively enhancing the mechanical properties of the aramid III fiber.

Description

Technical Field

[0001] This invention relates to the field of graphene application technology, and more specifically to whisker-modified sulfur-doped graphene-modified aramid III fibers and their preparation methods. Background Technology

[0002] Aramid III fiber is a para-aromatic polyamide fiber with a heterocyclic main chain, possessing excellent physicochemical properties such as lightweight, high strength, good impact resistance, high temperature resistance, and corrosion resistance. Currently, research on improving the mechanical properties of aramid III fiber mainly focuses on structural modification and surface modification. Structural modification primarily involves introducing new flexible groups such as ether bonds and silicon bonds into the molecular backbone to effectively improve fiber processability and increase molecular chain orientation, thereby enhancing mechanical properties. Surface modification often employs methods such as plasma treatment, coupling agents, and surface coating to improve the affinity between the fiber and the matrix, thus enhancing the overall performance of the composite material. However, most current modification methods do not significantly improve the mechanical properties of aramid III fiber. Therefore, further research is needed to improve the mechanical properties of aramid III fiber. Graphene, on the other hand, is an ideal polymer reinforcement material due to its unique sp... 2 The structure has a theoretical tensile strength of up to 130 GPa and an elastic modulus of up to 1000 GPa. For most fibers, such as nylon 6, polyimide, and polyvinyl alcohol, the tensile strength can be increased by 20% to 50% and the elastic modulus can even be doubled by adding graphene.

[0003] Currently, the use of graphene to reinforce aramid fibers only involves coating the surface of the aramid fibers with graphene. This results in weak interactions between graphene and aramid polymer molecules, and the graphene is prone to detachment, failing to significantly improve the mechanical properties of graphene / aramid composite fibers. Furthermore, aramid III molecules have a one-dimensional linear structure, capable of oriented alignment under stretching, exhibiting a certain degree of crystallinity and orientation. However, this crystallinity and orientation are not high, and the weak interactions between aramid III molecules contribute to defects in the fiber's internal structure, resulting in insufficient density and consequently poor mechanical properties. Therefore, improving the mechanical properties of aramid III is a pressing issue that needs to be addressed. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention provides a method for preparing short-fiberized whisker-shaped sulfur-doped graphene suitable for reinforcing aramid III fibers.

[0005] In one aspect, the present invention provides a modified aramid III fiber, which comprises whisker-like sulfur-doped graphene with a length of 50 nm to 20 μm.

[0006] According to one embodiment of the present invention, the sulfur doping content of the whisker-like sulfur-doped graphene is 1 atom%-4.56 atom%.

[0007] According to another embodiment of the invention, the whisker-shaped sulfur-doped graphene is a mixture of different lengths in any proportion.

[0008] According to another embodiment of the present invention, the length of the whisker-like graphene is 150 nm.

[0009] According to another embodiment of the present invention, the amount of whisker-shaped sulfur-doped graphene is 0.01%-0.5wt% of the total mass of the modified aramid III fiber, which is 100%.

[0010] According to another embodiment of the present invention, the breaking strength is 33-35 cN / dtex, the elastic modulus is 850-1000 cN / dtex, and the elongation at break is 4.0-4.5%.

[0011] Another aspect of the present invention provides a method for preparing the modified aramid III fiber, comprising: S1, preparing whisker-shaped sulfur-doped graphene; S2, subjecting the prepared whisker-shaped sulfur-doped graphene to short fiberization to obtain whisker-shaped sulfur-doped graphene of a predetermined size; S3, dispersing the short-fiberized whisker-shaped sulfur-doped graphene in N,N-dimethylacetamide to form a dispersion; S4, adding the dispersion to an N,N-dimethylacetamide solution containing monomers forming aramid III, and performing a polymerization reaction to obtain a polymer solution; and S5, spinning the polymer solution to obtain modified aramid III fiber.

[0012] According to one embodiment of the present invention, the mass content of the whisker-like sulfur-doped graphene in the dispersion is 0.01-1.25 g / mL. -1 .

[0013] This invention first obtains a whisker-like template agent via a homogeneous hydrothermal method, then obtains whisker-like sulfur-doped graphene via vapor deposition, and finally obtains short-fiberized whisker-like sulfur-doped graphene via a homogeneous pulverization method. This graphene can be uniformly dispersed in the organic solvent N,N-dimethylacetamide (DMAc) to obtain a uniform and stable graphene dispersion. Furthermore, by adding the graphene in situ, it participates in the entire polycondensation reaction. The sulfur element contained in the graphene can form chemical bonds with the acyl chloride groups in the polymer monomer, achieving efficient and tight bonding between graphene and aramid molecules, enhancing the intermolecular forces between aramid polymer chains. Simultaneously, this graphene possesses a one-dimensional linear structure similar to aramid III molecular chains, which can better induce the crystallization and orientation of aramid III molecules during spinning, thereby comprehensively improving the mechanical properties of aramid fibers.

[0014] The advantages of this invention are: a simple, low-cost, and environmentally friendly homogeneous hydrothermal method is used to obtain a whisker-like template agent, followed by vapor deposition to obtain whisker-like sulfur-doped graphene, and finally, homogenization and pulverization to obtain a series of whisker-like sulfur-doped graphenes with different aspect ratios. Among these, the short-fiberized whisker-like graphene exhibits excellent dispersibility in DMAc. It not only enhances the intermolecular forces of aramid III molecules and fills internal structural defects in aramid III, but also induces the crystallization and orientation of aramid III during spinning and drawing, thereby comprehensively improving the mechanical properties of aramid III fibers. The entire preparation process of short-fiberized whisker-like sulfur-doped graphene is simple, low-cost, and environmentally friendly, and can be used for mass production.

[0015] Therefore, this invention uses whisker-shaped sulfur-doped graphene as a reinforcement for aramid III fibers. Through in-situ polymerization, the whisker-shaped structure of the graphene is used to induce further crystallization and orientation of aramid III. At the same time, the doped sulfur element can improve the dispersibility of graphene in DMAC and enhance the hydrogen bonds between it and the aramid III backbone. This not only enhances the interaction between aramid III molecular chains but also plays a densifying role, thereby comprehensively enhancing the mechanical properties of aramid III fibers. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the synthesis of whisker-shaped sulfur-doped graphene in Example 1.

[0017] Figure 2 The image shows the characterization of the whisker-like sulfur-doped graphene in Example 1.

[0018] Figure 3 This is a particle size distribution diagram of the whisker-like sulfur-doped graphene in Example 1.

[0019] Figure 4 The image shows the dispersion of the whisker-like sulfur-doped graphene dispersion in Example 1 after standing for different number of days.

[0020] Figure 5 The images show scanning electron microscope (SEM) images of the graphene / aramid III composite fiber and the pure aramid fiber in Example 1.

[0021] Figure 6 The images show the XRD patterns of the graphene / aramid III composite fiber and the pure aramid fiber in Example 1. Detailed Implementation

[0022] The present invention will now be described in detail with reference to specific embodiments.

[0023] The modified aramid III fiber of this invention comprises whisker-like sulfur-doped graphene with a length of 50 nm to 20 μm. This invention uses whisker-like sulfur-doped graphene as a reinforcement for aramid III fibers, utilizing the whisker-like structure of the graphene to induce further crystallization and orientation of the aramid III. Simultaneously, the doped sulfur element can chemically bond with the acyl chloride groups in the polymer monomer, not only enhancing the intermolecular forces of the aramid III molecular chains but also playing a densifying role, thereby comprehensively enhancing the mechanical properties of the aramid III fiber.

[0024] In an optional embodiment, the sulfur doping content of the whisker-like sulfur-doped graphene is 1 atom% to 4.56 atom.

[0025] In an alternative embodiment, the whisker-shaped sulfur-doped graphene is a mixture of different lengths in any proportion.

[0026] In an optional embodiment, the length of the whisker-like graphene is 150 nm.

[0027] In an optional embodiment, the amount of whisker-shaped sulfur-doped graphene is 0.01%-0.5wt% of the total mass of the modified aramid III fiber, which is 100% of the total mass of the modified aramid III fiber.

[0028] According to another embodiment of the present invention, the breaking strength is 33-35 cN / dtex, the elastic modulus is 850-1000 cN / dtex, and the elongation at break is 4.0-4.5%.

[0029] Another aspect of the present invention provides a method for preparing the modified aramid III fiber, comprising: S1, preparing whisker-shaped sulfur-doped graphene; S2, subjecting the prepared whisker-shaped sulfur-doped graphene to short fiberization to obtain whisker-shaped sulfur-doped graphene of a predetermined size; S3, dispersing the short-fiberized whisker-shaped sulfur-doped graphene in N,N-dimethylacetamide to form a dispersion; S4, adding the dispersion to an N,N-dimethylacetamide solution containing monomers forming aramid III, and performing a polymerization reaction to obtain a polymer solution; and S5, spinning the polymer solution to obtain modified aramid III fiber.

[0030] In step S1, a specific example of preparing whisker-like sulfur-doped graphene can be described as follows: Hydrated magnesium sulfate, ammonia, and sodium dodecylbenzenesulfonate are dissolved in deionized water at a molar ratio of 5:2:1. The mixture is stirred for 30 min, and the solution is transferred to a 100 mL hydrothermal tank. In a homogeneous reactor, a homogeneous hydrothermal reaction is carried out at 200 °C for 20 h to obtain whisker-like magnesium sulfate template agent. Then, 30 g of the template agent is added to a vertical furnace, and argon gas (1.0 L / min) is introduced. -1 Once the temperature reaches 900℃, CH4 (0.5 L / min) is introduced. -1The product was subjected to vapor deposition for 15 minutes. After the reaction was completed, the product was acid-washed and purified to remove the template agent, and then filtered, washed and dried to obtain whisker-shaped sulfur-doped graphene powder.

[0031] In step S2, the whisker-like sulfur-doped graphene obtained in step S1 is homogenized and pulverized under high temperature and low pressure for 1-3 hours using a homogenizer to obtain a series of short-fiber whisker-like sulfur-doped graphene with different aspect ratios.

[0032] In step S3, short-fiberized whisker-shaped sulfur-doped graphene is dispersed in DMAc and ultrasonically treated for 1-2 hours to obtain a uniform and stable graphene dispersion. The mass fraction of graphene in this dispersion is 0.001-0.5%.

[0033] Finally, in steps S4 and S5, whisker-like graphene / aramid III composite fibers are prepared. A specific example can be as follows: LiCl cosolvent, p-phenylenediamine (PPD), 2-(4-aminophenyl)-5-aminobenzimidazole (DAPBI), and other polymerization monomers are added to DMAc and stirred under nitrogen until completely dissolved. The graphene dispersion prepared in (2) is added before the polymerization reaction occurs, allowing graphene to participate in the entire polymerization process. After the reactor temperature drops to 0-8℃, the first batch of terephthaloyl chloride (TPC) is added and stirred for 0.5-1h. Then, TPC is added in 2-5 batches, and stirred thoroughly for 1-2h to obtain the graphene / aramid III polymerization solution. Furthermore, by adjusting the amount of graphene added (0.001%-10%), polymerization solutions with different graphene contents are obtained. The LiCl content was 3.5 wt%, the molar ratio of TPC, PPD, and DAPBI was 1:0.4:0.6, and the polymer solid content was 4.2 wt%. The chemical formula for the polymerization process of aramid III is as follows:

[0034]

[0035] The graphene / aramid polymer solution is then subjected to vacuum degassing, followed by negative stretching, multi-stage coagulation bath, water washing, and drying. It is then placed in a heat treatment channel at 380-450℃ and treated under nitrogen for 1-3 minutes. Finally, it is wound into filaments to obtain graphene / aramid III composite fibers with a breaking strength of 33-36 cN / dtex, a breaking elongation of 4.0%-4.5%, and an elastic modulus of 850-1000 cN / dtex.

[0036] In an optional embodiment, the mass content of whisker-like sulfur-doped graphene in the dispersion is 0.01-1.25 g / mL. -1 .

[0037] As a further improvement of the present invention, the graphene dispersion can be any one or more of these short-fibered whisker-shaped sulfur-doped graphenes with different aspect ratios, mixed in any proportion.

[0038] The present invention will be further described below through specific examples. However, these examples are merely exemplary and do not constitute any limitation on the scope of protection of the present invention.

[0039] Unless otherwise specified, all reagents, materials and instruments used in the following examples and comparative examples are commercially available.

[0040] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments. However, the description of the embodiments is only a part of the embodiments of the present invention and is not limited thereto.

[0041] Example 1

[0042] Hydrated magnesium sulfate, ammonia, and sodium dodecylbenzenesulfonate were dissolved in deionized water at a molar ratio of 5:2:1 and stirred for 30 min. The solution was then transferred to a 100 mL hydrothermal tank and subjected to a homogeneous hydrothermal reaction at 200 °C for 20 h to obtain whisker-like magnesium sulfate template agent. 30 g of the template agent was then added to a vertical furnace, and argon gas (1.0 L·min⁻¹) was introduced. -1 Once the temperature reaches 900℃, CH4 (1.5 L·min) is introduced. -1 The product was subjected to vapor deposition for 15 minutes. After the reaction was completed, the product was acid-washed and purified to remove the template agent, and then filtered, washed and dried to obtain whisker-shaped sulfur-doped graphene powder.

[0043] The obtained graphene was homogenized in a homogenizer under high temperature and low pressure for 3 hours to obtain whisker-like sulfur-doped graphene with a length of 150 nm. This graphene was then dispersed in DMAC and ultrasonically treated for 2 hours to obtain a uniform and stable dispersion with a concentration of 0.125 g / mL of whisker-like sulfur-doped graphene. -1 .

[0044] LiCl co-solvent, p-phenylenediamine (PPD), 2-(4-aminophenyl)-5-aminobenzimidazole (DAPBI), and terephthaloyl chloride (TPC) were added to DMAc and stirred under nitrogen until completely dissolved. The prepared graphene dispersion was added before the polymerization reaction to ensure that the whisker-like sulfur-doped graphene participated in the entire polymerization process. After the reactor temperature dropped to 8°C, the first batch of terephthaloyl chloride (TPC) was added and stirred for 1 hour. Then, TPC was added in five more batches, and the mixture was stirred thoroughly for 2 hours to obtain the graphene / aramid III polymerization solution. The amount of LiCl used was 3.5 wt%, the molar ratio of TPC, PPD, and DAPBI was 1:0.4:0.6, and the polymer solid content was 4.2 wt%. The content of whisker-like sulfur-doped graphene in the fiber was 0.05 wt%, and the sulfur doping amount was 4.56 atom.

[0045] The obtained polymerization solution was subjected to a series of steps including primary coagulation bath, secondary coagulation bath, washing, drying, hot stretching, oiling, and winding. The negative stretching ratio in the primary coagulation bath was -0.7, the stretching ratio in the secondary coagulation bath was 2.5, and conventional spinning parameters such as no stretching ratio during washing and a hot stretching ratio of 1.05 were used to prepare modified aramid III fibers. The fiber was tested and found to have a breaking strength of 34.76 cN / dTex, a tensile modulus of 921.97 cN / dTex, and an elongation at break of 4.08%.

[0046] Example 2

[0047] Sulfur-doped graphene with whisker-like structures approximately 150 nm in length was dispersed in DMAC, resulting in a graphene dispersion with a concentration of 0.1875 g / mL. -1 Graphene dispersion was added in situ during the polymerization of aramid III to obtain a graphene / aramid polymerization solution. This solution was then spun to prepare graphene / aramid III composite fibers. The fiber contained 0.075 wt% whisker-like sulfur-doped graphene, had a tensile strength of 34.06 cN / dTex, a tensile modulus of 893.54 cN / dTex, and an elongation at break of 4.01%.

[0048] Example 3

[0049] Sulfur-doped graphene with whisker-like crystals approximately 150 nm in length was dispersed in DMAC, resulting in a graphene dispersion with a concentration of 0.0625 g / mL. -1 Graphene dispersion was added in situ during the polymerization of aramid III to obtain a graphene / aramid polymerization solution. This solution was then spun to prepare graphene / aramid III composite fibers. The fiber contained 0.025 wt% whisker-like sulfur-doped graphene, had a tensile strength of 33.25 cN / dTex, a tensile modulus of 848.16 cN / dTex, and an elongation at break of 3.94%.

[0050] Example 4

[0051] Sulfur-doped graphene with whisker-like structures approximately 150 nm in length was dispersed in DMAC, resulting in a graphene dispersion with a concentration of 0.125 g / mL. -1 Graphene dispersion was added in situ during the polymerization of aramid III to obtain a graphene / aramid polymerization solution. This solution was then spun to prepare graphene / aramid III composite fibers. The fiber contained 0.05 wt% whisker-like sulfur-doped graphene and 2 atm% sulfur doping. Its tensile strength was 33.72 cN / dTex, its tensile modulus was 857.85 cN / dTex, and its elongation at break was 4.04%.

[0052] Example 5

[0053] Sulfur-doped graphene with whisker-like structures approximately 150 nm in length was dispersed in DMAC, resulting in a graphene dispersion with a concentration of 1.25 g / mL. -1 Graphene dispersion was added in situ during the polymerization of aramid III to obtain a graphene / aramid polymerization solution. This solution was then spun to prepare graphene / aramid III composite fibers. The fibers contained 0.5 wt% whisker-like sulfur-doped graphene and 4.56 atom% sulfur doping. Their tensile strength was 31.55 cN / dTex, tensile modulus was 814.15 cN / dTex, and elongation at break was 4.06%.

[0054] Example 6

[0055] Sulfur-doped graphene with whisker-like crystals approximately 20 μm in length was dispersed in DMAC, resulting in a graphene dispersion with a concentration of 0.125 g / mL. -1 Graphene dispersion was added in situ during the polymerization of aramid III to obtain a graphene / aramid polymerization solution. This solution was then spun to prepare graphene / aramid III composite fibers. The fiber contained 0.05 wt% whisker-like sulfur-doped graphene and 4.56 atom% sulfur doping. Its tensile strength was 32.46 cN / dTex, its tensile modulus was 838.49 cN / dTex, and its elongation at break was 4.01%.

[0056] Example 7

[0057] Sulfur-doped graphene with whisker-like structures approximately 150 nm in length was dispersed in DMAC, resulting in a graphene dispersion with a concentration of 0.125 g / mL. -1Graphene dispersion was added in situ during the polymerization of aramid III to obtain a graphene / aramid polymerization solution. This solution was then spun to prepare graphene / aramid III composite fibers. The fiber contained 0.05 wt% whisker-like sulfur-doped graphene and 1 atm% sulfur doping. Its tensile strength was 33.04 cN / dTex, its tensile modulus was 843.26 cN / dTex, and its elongation at break was 4.03%.

[0058] Comparative Example 1

[0059] Sulfur-doped graphene with a length of 50 μm was dispersed in DMAC to obtain a graphene dispersion with a concentration of 0.125 g / mL. -1 Graphene dispersion was added in situ during the polymerization of aramid III to obtain graphene / aramid polymerization solution, which was then spun to prepare graphene / aramid III composite fiber. The fiber had a breaking strength of 30.72 cN / dTex, a tensile modulus of 818.78 cN / dTex, and an elongation at break of 3.88%.

[0060] Comparative Example 2

[0061] 50 μm long whisker-shaped graphene was dispersed in DMAC to obtain a graphene dispersion with a concentration of 0.125 g / mL. -1 Graphene dispersion was added in situ during the polymerization of aramid III to obtain a graphene / aramid polymer solution, which was then spun to prepare graphene / aramid III composite fiber. The fiber had a breaking strength of 28.56 cN / dTex, a tensile modulus of 801.15 cN / dTex, and an elongation at break of 3.84%.

[0062] Comparative Example 3

[0063] Sulfur-doped graphene with a length of 50 μm was dispersed in DMAC to obtain a graphene dispersion with a concentration of 0.125 g / mL. -1 The graphene dispersion was added near the end of the aramid III polymerization reaction, and the mixture was stirred for another 1-2 hours to obtain a graphene / aramid polymerization solution. This solution was then spun to prepare graphene / aramid III composite fibers, which had a breaking strength of 27.87 cN / dTex, a tensile modulus of 786.34 cN / dTex, and an elongation at break of 3.75%.

[0064] The parameters and test results of Examples 1-7 and Comparative Examples 1-3 are shown in Table 1 below.

[0065] Table 1

[0066]

[0067]

[0068] from Figure 1-6 As can be seen, S-doped whisker-like graphene was obtained by combining a simple hydrothermal method and a CVD method. This graphene has a uniform and relatively long size and a certain amount of S doping. After short-fibering treatment, uniform graphene with a size of hundreds of nanometers was obtained. This short-fibered graphene exhibits good dispersibility in DMAc. Adding the short-fibered S-doped graphene whiskers in situ to the polymerization system of aramid III can induce crystallization and orientation, thereby making the fibers denser and improving their performance.

[0069] Table 1 shows that when the graphene length is 150 nm, the S doping amount is 4.56 atom%, and the concentration of the graphene / DMAc dispersion is 0.125 g / mL -1 At that time, the composite fiber obtained after in-situ polymerization and spinning exhibited the best mechanical properties; under the same length and S doping amount, the mechanical properties of the composite fiber increased with the addition of graphene dispersion greater than 0.125 g / mL. -1 The tensile strength, elastic modulus, and elongation at break of the composite fiber gradually decrease; when the S doping amount and graphene dispersion concentration are constant, the mechanical properties of the composite fiber decrease with the increase of graphene length; when the graphene length and graphene dispersion concentration are constant, the mechanical properties of the composite fiber increase with the increase of S doping amount; when other parameters remain unchanged and only the polymerization method is changed, the mechanical properties of the graphene / aramid III composite fiber obtained by in-situ polymerization are significantly better than those obtained by adding graphene later.

[0070] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing modified aramid III fiber, characterized in that, include: S1, preparation of whisker-shaped sulfur-doped graphene; S2, the prepared whisker-shaped sulfur-doped graphene is subjected to short fiberization treatment to obtain whisker-shaped sulfur-doped graphene of a predetermined size. S3, disperse the short-fiberized whisker-shaped sulfur-doped graphene in N,N-dimethylacetamide to form a dispersion; S4, the dispersion is added to an N,N-dimethylacetamide solution containing monomers that form aramid III, and a polymerization reaction is carried out to obtain a polymer solution; S5, the polymerization solution is spun to obtain modified aramid III fibers; The modified aramid III fiber comprises whisker-shaped sulfur-doped graphene with a length of 150 nm to 20 μm, wherein the sulfur doping content of the whisker-shaped sulfur-doped graphene is 1 atom% to 4.56 atom%. Based on the total mass of the modified aramid III fiber as 100%, the amount of whisker-shaped sulfur-doped graphene accounts for 0.01%-0.5wt% of the modified aramid III composite fiber.

2. The preparation method according to claim 1, characterized in that, The mass content of the whisker-shaped sulfur-doped graphene in the dispersion is 0.01-1.25 g / mL. -1 .

3. The preparation method according to claim 1, characterized in that, The whisker-shaped sulfur-doped graphene is a mixture of different lengths in any proportion.

4. The preparation method according to claim 3, characterized in that, The whisker-shaped graphene has a length of 150 nm.

5. A modified aramid III fiber, characterized in that, Prepared by the preparation method according to any one of claims 1-4.

6. The modified aramid III fiber according to claim 5, characterized in that, The modified aramid III fiber has a breaking strength of 33-35 cN / dtex, an elastic modulus of 850-1000 cN / dtex, and an elongation at break of 4.0-4.5%.

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