Preparation method of single-layer graphene oxide-reinforced high-strength and high-toughness heterocyclic aramid fiber

Abstract

The present invention provides a method for preparing a high-strength and high-toughness heterocyclic aramid fiber reinforced by single-layer graphene oxide. In the present invention, heterocyclic para-aramid is selected, and a trace amount of graphene oxide is directly introduced into the spinning solution of the heterocyclic para-aramid polymer. During the coagulation and stretching processes of the aramid, the graphene oxide with a rigid macromolecular structure approaches the aramid molecules continuously. After reaching a certain distance, hydrogen bonds are formed between the graphene oxide and the aramid chain-like molecules, fixing the aramid molecules, preventing the aramid from retracting and the lubrication between the aramid molecules, and improving the draw ratio and orientation degree of the heterocyclic aramid. Through subsequent steps such as stretching and heat treatment, highly oriented heterocyclic aramid is obtained, with a breaking strength of up to 6.28 GPa, an elastic modulus of 120 GPa, and an elongation at break of 5.5%.

Description

Technical Field

[0001] The present invention relates to a preparation method of graphene oxide-reinforced high-strength heterocyclic aramid fiber. By adding a trace amount of graphene oxide to the spinning solution of the heterocyclic aramid polymer, the mechanical properties of the heterocyclic aramid are improved. Background Art

[0002] Aramid fibers mainly include wholly aromatic polyamide fibers and heterocyclic aromatic polyamide fibers, and can be divided into three types: ortho-aramid, para-aramid (PPTA), and meta-aramid (PMTA). Among them, heterocyclic aromatic polyamide fiber is abbreviated as heterocyclic aramid or aramid III, which is a high-performance organic fiber with high strength, high modulus, and excellent heat resistance, creep resistance, and dielectric properties.

[0003] Currently, the improvement of the mechanical properties of heterocyclic aramid is mainly achieved by introducing other modified monomers for quaternary copolymerization modification on the basis of the existing molecular structure of heterocyclic aramid. The mechanism of this method is to select diamine monomers containing polar side groups, such as 2-chloro-p-phenylenediamine, 2,5-diaminobenzonitrile, etc. The introduction of polar groups significantly improves the composite properties of heterocyclic aramid, thereby increasing its use strength after dipping. However, the introduction of polar side groups reduces the thermal stability of heterocyclic aramid, limiting its application in some fields.

[0004] Graphene is one of the thinnest and strongest materials currently known, and also has good toughness and very good thermal conductivity. By introducing graphene into heterocyclic aramid, its mechanical properties and thermal properties will be more excellent, meeting the application requirements of different fields. However, directly introducing graphene oxide into the heterocyclic aramid polymer solution, this blending method is generally limited to physical blending. On the one hand, it is often impossible to achieve high-concentration doping, and on the other hand, it cannot effectively improve its performance. And adding graphene oxide or amino-functionalized graphene as monomers to the polymerization reaction solution of heterocyclic aramid is difficult to control the reaction, which will ultimately affect the stability of the mechanical properties of heterocyclic aramid fibers. Summary of the Invention

[0005] The present invention aims at the problems in the background art and provides a method for preparing high-strength heterocyclic aramid fibers. The present invention selects heterocyclic para-aramid, and directly introduces a small amount of graphene oxide into the spinning solution of the heterocyclic para-aramid polymer. Heterocyclic para-aramid is a flexible chain-like polymer, and its natural state tends to curl, especially in a solvent, where it is in a random curled state. Graphene oxide is a sheet-like molecule with a rigid macromolecular structure. When sheet-like graphene oxide is added between the aramid molecular chains, during the coagulation and stretching processes, graphene oxide continuously approaches the aramid molecules. After reaching a certain distance, hydrogen bonds are formed between the sheet-like graphene oxide molecules and the aramid chain-like molecules. The sheet-like graphene oxide plays a role in fixing the aramid molecules to prevent retraction and lubricating between the aramid molecules, improving the draw ratio and orientation degree of the heterocyclic aramid. Through subsequent steps such as stretching and heat treatment, highly oriented heterocyclic aramid is obtained, with a breaking strength of up to 6.28 GPa, an elastic modulus of 120 GPa, and an elongation at break of 5.5%.

[0006] Specifically, the present invention adopts the following technical solution: A method for preparing aramid fibers, comprising the following steps:

[0007] (1) Disperse single-layer graphene oxide with a size of 2 - 5 μm in a dimethylacetamide solution, add the dimethylacetamide solution of the heterocyclic para-aramid polymer, adjust the solid content, and uniformly stir to obtain a spinning solution with a heterocyclic aramid solid content of 2 wt% and the proportion of graphene oxide accounting for the mass of the aramid being . In this step, para-aramid containing heterocycles is used to enhance the flexibility and polarity of the aramid molecules, so that they can be dissolved in the DMAC polar solvent; the oxygen-containing functional groups in graphene oxide enhance the polarity of graphene oxide, enabling graphene oxide to also be dissolved in the DMAC polar solvent. Since the solvents of the two are the same, it provides conditions for their blending. Graphene oxide needs to be single-layer. If it is multi-layer, the tightness between the aramid molecules will be reduced. The size of graphene oxide is most suitable at about 2 - 5 μm, which is adapted to the size of the heterocyclic para-aramid molecules. For example, in a reinforced cement board with steel bars, the cement particle size is about 10 μm, and the most suitable diameter of the steel bars is 10 - 30 mm; the diameter of the aramid molecules is about 2 nm, and the suitable size of GO is 2 - 5 μm. If the size is too large, too many aramid molecular chains will be connected, and the lubricating and fixing effects will be weakened.

[0008] (2) The spinning solution is defoamed and then spun. During spinning, the polymer solution is sprayed into a coagulation bath through a spinneret with a pore diameter of 0.4 - 1.0 mm to form nascent fibers. The coagulation bath is an aqueous alcohol solution with a volume fraction of 30% - 40%; the alcohol is one or more of methanol, ethanol, propanol, sec-butanol, and isobutanol; in this step, the density of the 30% - 40% aqueous alcohol solution is equivalent to or slightly greater than that of the aramid solution prepared in step 1, so as to ensure that the nascent fibers maintain a good state and are drawn out of the coagulation bath with the least force, laying a foundation for subsequent high strength.

[0009] (3) The nascent fibers enter a stretching bath, which is deionized water, and the stretching ratio is 2.1 - 2.4 times;

[0010] (4) After washing with water and drying, heat treatment is carried out in an air atmosphere at 340 - 440 °C for 1 - 20 minutes to obtain high-strength aramid fibers. In this step, after high-temperature heat treatment, GO is tightly combined with the surrounding aramid molecules and crystallizes. Since GO is monolayer and small in size, although the proportion is small, the number is large, so that a large number of amorphous regions are crystallized, improving the crystallinity of the fiber and the connection points in the amorphous regions.

[0011] In some embodiments of the present application, the heterocyclic para-aramid polymer refers to poly(p-phenylene benzimidazole terephthalamide), especially poly(terephthaloyl terephthylenediamine) containing 2-(4-aminophenyl)-5-aminobenzimidazole.

[0012] In some embodiments of the present application, in step 1, in the N,N-dimethylacetamide solution of graphene oxide, the mass fraction of graphene oxide is

[0013] In some embodiments of the present application, in step 4, washing with water is carried out using deionized water at 70 °C.

[0014] In some embodiments of the present application, in step 4, first dry in an air atmosphere at 80 °C for 40 min, and then dry in an air atmosphere at 150 °C for 30 min.

[0015] The single-layer graphene oxide described in the present invention refers to graphene oxide raw materials with a monolayer ratio greater than 99.5%.

[0016] Compared with the prior art, the progress of the present invention is as follows:

[0017] Through physical doping of single-layer graphene oxide, the present invention realizes chemical induction during the high-temperature process, resulting in a qualitative change in the modification of aramid fibers. The breaking strength can reach 6.28 GPa, the elastic modulus reaches 120 GPa, and the elongation at break is 5.5%. The mechanical properties of the fibers are more stable. In addition, the preparation process of the present invention is easier to control and the cost is lower. Description of the Drawings

[0018] Figure 1 This is the process flow chart of the present invention.

[0019] Figure 2 This is the load-bearing test of aramid monofilaments under different GO ratios. Detailed implementation manners

[0020] The following is a detailed description of the present invention in combination with specific examples. These examples are completely illustrative and are only used to specifically describe the present invention, rather than limiting the present invention.

[0021] As Figure 1 shown, the continuous process flow chart of the present invention is provided, which includes:

[0022] (1) Dispersing single-layer graphene oxide with a size of 2-5 μm in a dimethylacetamide solution, adding a dimethylacetamide solution of a heterocyclic para-aramid polymer, adjusting the solid content, and uniformly stirring to obtain a spinning solution with a heterocyclic aramid solid content of 2 wt% and the proportion of graphene oxide in the aramid mass being ;

[0023] In the embodiment of the present invention, the heterocyclic para-aramid polymer refers to poly(p-phenylenebenzimidazole terephthalamide), especially poly(terephthaloyl terephthylenediamine) containing 2-(4-aminophenyl)-5-aminobenzimidazole, which can be prepared by the method described in 201010108545.6, and its structural formula is:

[0024]

[0025] where the ratio of m to n is less than or equal to 1.

[0026] (2) After the spinning solution is degassed, spinning is carried out. During spinning, the polymer solution is sprayed into a coagulation bath through a spinneret with a pore diameter of 0.4-1.0 mm to form nascent fibers, and the coagulation bath is an aqueous alcohol solution with a volume fraction of 30%-40%; the alcohol is one or more of methanol, ethanol, propanol, sec-butanol, and isobutanol;

[0027] (3) The nascent fibers enter a stretching bath, the stretching bath is deionized water, and the stretching ratio is 2.1-2.4 times;

[0028] (4) After washing with water and drying, heat treatment is carried out in an air atmosphere at 340-440 °C for 1-20 minutes to obtain high-strength aramid fibers.

[0029] The following is a further description of the present invention in combination with examples.

[0030] In the following examples, unless otherwise specified, the structural formula of poly(p-phenylenebenzimidazole terephthalamide) used is:

[0031]

[0032] Wherein the ratio of m to n is less than or equal to 1.

[0033] Example 1:

[0034] The graphene oxide used is monolayer graphene oxide with a monolayer rate greater than 99.5% and a warp dimension of 2 - 5 μm. The monolayer graphene oxide is dispersed in a dimethylacetamide solution to obtain a graphene oxide dispersion with a solid content of one ten-thousandth.

[0035] Then, the graphene oxide dispersion is compounded with a poly(p-phenylene benzobisoxazole terephthalamide) solution with a solid content of 4 wt%, and the solid content is adjusted using dimethylacetamide. After uniform stirring, a spinning solution with a heterocyclic aramid solid content of 2 wt% and a proportion of graphene oxide in aramid of is obtained.

[0036] The spinning solution is degassed and then spun. During spinning, the polymer solution is sprayed into a coagulation bath through a spinneret with a pore diameter of 0.4 mm to form a nascent fiber. The coagulation bath is an aqueous ethanol solution with a volume fraction of 30%. Then the nascent fiber enters a stretching bath, which is deionized water, and the stretching ratio is 2.2 times. Then it is washed with deionized water at 70°C. Then it is dried continuously in a two-stage non-contact manner in a tube furnace under an air atmosphere, which are drying at 80°C for 40 min and drying at 150°C for 30 min respectively. Finally, it is heat-treated continuously in a non-contact manner in a tube furnace under an air atmosphere at a temperature of 340°C for 20 minutes.

[0037] The aramid fiber prepared in this example has a breaking strength of 5.69 GPa, an elastic modulus of 109.4 GPa, and an elongation at break of 5.2%.

[0038] Example 2:

[0039] The graphene oxide used is monolayer graphene oxide with a monolayer rate greater than 99.5% and a warp dimension of 2 - 5 μm. The monolayer graphene oxide is dispersed in a dimethylacetamide solution to obtain a graphene oxide dispersion with a solid content of one ten-thousandth.

[0040] Then, the graphene oxide dispersion is compounded with a poly(p-phenylene benzobisoxazole terephthalamide) solution with a solid content of 4%, and the solid content is adjusted using dimethylacetamide. After uniform stirring, a heterocyclic aramid solid content of 2% and a proportion of graphene oxide in aramid of Spinning solution. The spinning solution is degassed and then spun. During spinning, the polymer solution is sprayed through a spinneret with a pore diameter of 0.4 mm into a coagulation bath to form nascent fibers. The coagulation bath is an aqueous methanol solution with a volume fraction of 40%. Then the nascent fibers enter a stretching bath, which is deionized water, and the stretching ratio is 2.3 times. Then, washing is carried out with deionized water at 70 °C. After that, it passes through a tube furnace for two-stage continuous non-contact drying in an air atmosphere, which are drying at 80 °C for 40 min and drying at 150 °C for 30 min respectively. Finally, it passes through a tube furnace for continuous non-contact heat treatment in an air atmosphere at a temperature of 400 °C for 1 minute.

[0041] The aramid fiber prepared in this example has a breaking strength of 6.04 GPa, an elastic modulus of 118.5 GPa, and an elongation at break of 5.1%.

[0042] Example 3:

[0043] The graphene oxide used is monolayer graphene oxide with a monolayer rate greater than 99.5% and a longitudinal dimension of 2 - 5 μm. The monolayer graphene oxide is dispersed in a dimethylacetamide solution to obtain a graphene oxide dispersion with a solid content of one ten-thousandth.

[0044] Then, the graphene oxide dispersion is compounded with a poly(p - benzimidazole terephthalamide) solution with a solid content of 4%, and the solid content is adjusted with dimethylacetamide. After uniform stirring, a spinning solution with a heterocyclic aramid solid content of 2% and a proportion of graphene oxide in aramid of is obtained. The spinning solution is degassed and then spun. During spinning, the polymer solution is sprayed through a spinneret with a pore diameter of 0.4 mm into a coagulation bath to form nascent fibers. The coagulation bath is an aqueous propanol solution with a volume fraction of 30%. Then the nascent fibers enter a stretching bath, which is deionized water, and the stretching ratio is 2.4 times. Then, washing is carried out with deionized water at 70 °C. After that, it passes through a tube furnace for two-stage continuous non-contact drying in an air atmosphere, which are drying at 80 °C for 40 min and drying at 150 °C for 30 min respectively. Finally, it passes through a tube furnace for continuous non-contact heat treatment in an air atmosphere at a temperature of 340 °C for 20 minutes.

[0045] The aramid fiber prepared in this example has a breaking strength of 6.28 GPa, and the weight that a single filament can bear is above 760 g (such as Figure 2 )), an elastic modulus of 114.2 GPa, and an elongation at break of 5.5%.

[0046] Example 4:

[0047] The graphene oxide used is monolayer graphene oxide with a monolayer ratio greater than 99.5% and a warp size of 2 - 5 μm. The monolayer graphene oxide is dispersed in a dimethylacetamide solution to obtain a graphene oxide dispersion with a solid content of one ten-thousandth.

[0048] Then, this graphene oxide dispersion is compounded with a poly(p - phenylene benzimidazole terephthalamide) solution with a solid content of 4%, and dimethylacetamide is used to adjust its solid content. After uniform stirring, a spinning solution with a heterocyclic aramid solid content of 2% and the proportion of graphene oxide in aramid being is obtained. After the spinning solution is degassed, spinning is carried out. During spinning, the polymer solution is sprayed into a coagulation bath through a spinneret with a pore diameter of 1.0 mm to form nascent fibers. The coagulation bath is an aqueous ethanol solution with a volume fraction of 30%. Then the nascent fibers enter a stretching bath, which is deionized water, and the stretching ratio is 2.3 times. Then water washing is carried out, and 70°C deionized water is used for water washing. Then it undergoes two - stage continuous non - contact drying in a tube furnace under an air atmosphere, which are drying at 80°C for 40 min and drying at 150°C for 30 min respectively. Finally, it undergoes continuous non - contact heat treatment in a tube furnace under an air atmosphere at a temperature of 340°C for 20 minutes.

[0049] The aramid fiber prepared in this example has a breaking strength of 5.92 GPa, an elastic modulus of 107.7 GPa, and an elongation at break of 5.5%.

[0050] Example 5:

[0051] The graphene oxide used is monolayer graphene oxide with a monolayer ratio greater than 99.5% and a warp size of 2 - 5 μm. The monolayer graphene oxide is dispersed in a dimethylacetamide solution to obtain a graphene oxide dispersion with a solid content of one ten - thousandth.

[0052] Then, this graphene oxide dispersion is compounded with a poly(p - phenylene benzimidazole terephthalamide) solution with a solid content of 4%, and dimethylacetamide is used to adjust its solid content. After uniform stirring, a spinning solution with a heterocyclic aramid solid content of 2% and the proportion of graphene oxide in aramid being The spinning solution. After degassing treatment, the spinning solution is spun. During spinning, the polymer solution is sprayed into a coagulation bath through a spinneret with a pore diameter of 0.5 mm to form nascent fibers. The coagulation bath is an aqueous solution of methanol / ethanol with a volume fraction of 30%, where the volume ratio of methanol / ethanol is 1 / 1. Then the nascent fibers enter a stretching bath, which is deionized water, and the stretching ratio is 2.2 times. After that, washing is carried out with deionized water at 70 °C. Then it undergoes two-stage continuous non-contact drying in a tubular furnace under an air atmosphere, which are drying at 80 °C for 40 min and drying at 150 °C for 30 min respectively. Finally, it undergoes continuous non-contact heat treatment in a tubular furnace under an air atmosphere at a temperature of 350 °C for 17 minutes. The aramid fiber prepared by this method has a breaking strength of 5.8 GPa, an elastic modulus of 128.9 GPa, and an elongation at break of 4.5%.

[0053] Example 6:

[0054] The graphene oxide used is monolayer graphene oxide, with a monolayer rate greater than 99.5% and a longitudinal size of 2 - 5 μm. The monolayer graphene oxide is dispersed in a dimethylacetamide solution to obtain a graphene oxide dispersion with a solid content of one ten-thousandth.

[0055] Then the graphene oxide dispersion is compounded with a poly(p - phenylene benzimidazole terephthalamide) solution with a solid content of 4%, and dimethylacetamide is used to adjust its solid content. After uniform stirring, a spinning solution with a heterocyclic aramid solid content of 2% and the proportion of graphene oxide in aramid being The spinning solution. After degassing treatment, the spinning solution is spun. During spinning, the polymer solution is sprayed into a coagulation bath through a spinneret with a pore diameter of 0.5 mm to form nascent fibers. The coagulation bath is an aqueous solution of ethanol with a volume fraction of 30%. Then the nascent fibers enter a stretching bath, which is deionized water, and the stretching ratio is 2.4 times. After that, washing is carried out with deionized water at 70 °C. Then it undergoes two-stage continuous non-contact drying in a tubular furnace under an air atmosphere, which are drying at 80 °C for 40 min and drying at 150 °C for 30 min respectively. Finally, it undergoes continuous non-contact heat treatment in a tubular furnace under an air atmosphere at a temperature of 400 °C for 5 minutes.

[0056] The aramid fiber prepared by this method has a breaking strength of 5.65 GPa, an elastic modulus of 125.5 GPa, and an elongation at break of 4.5%.

[0057] Comparative Example 1

[0058] The poly(p-phenylene benzobisoxazole terephthalamide) solution with a solid content of 4% was diluted with dimethylacetamide. After uniform stirring, a heterocyclic aramid spinning solution with a solid content of 2% was obtained. After degassing, the spinning solution was wet-spun. During spinning, the polymer solution was sprayed through a spinneret with a pore diameter of 0.5 mm into a coagulation bath to form nascent fibers. The coagulation bath was an aqueous ethanol solution with a volume fraction of 30%. Subsequently, the nascent fibers entered a stretching bath, which was deionized water, and the stretching ratio was 2.0 times. Then, washing was carried out with deionized water at 70 °C. After that, two-stage continuous non-contact drying was carried out in a tube furnace under an air atmosphere, which were drying at 80 °C for 40 min and drying at 150 °C for 30 min respectively. Finally, continuous non-contact heat treatment was carried out in a tube furnace under an air atmosphere at a temperature of 350 °C for 17 minutes. The aramid fibers prepared by this method had a breaking strength of 5.4 GPa, an elastic modulus of 122.2 GPa, and an elongation at break of 4.5%.

Claims

1. A preparation method of single-layer graphene oxide-reinforced high-strength and high-toughness heterocyclic aramid fiber, characterized in that, it comprises the following steps: (1)Disperse single-layer graphene oxide with a size of 2-5 μm in a dimethylacetamide solution, add a dimethylacetamide solution of heterocyclic para-aramid polymer, adjust the solid content, and obtain a spinning solution with a heterocyclic para-aramid solid content of 2 wt% after uniform stirring. The proportion of graphene oxide in the aramid mass is ; (2) The spinning solution is degassed and then spun; during spinning, the polymer solution is sprayed into a coagulation bath through a spinneret with a pore diameter of 0.4 - 1.0 mm to form nascent fibers, and the coagulation bath is an aqueous alcohol solution with a volume fraction of 30% - 40%; the alcohol is one or more of methanol, ethanol, propanol, sec-butanol, and isobutanol; (3) The nascent fibers enter a stretching bath, the stretching bath is deionized water, and the stretching ratio is 2.1 - 2.4 times; (4) After washing with water and drying, heat treatment is carried out in an air atmosphere at 340 - 440 °C for 1 - 20 minutes to obtain high-strength aramid fiber. In step 4, first dry in an air atmosphere at 80 °C for 40 min, and then dry in an air atmosphere at 150 °C for 30 min.

2. The preparation method according to claim 1, characterized in that, the heterocyclic para-aramid polymer is poly(p-phenylene terephthalamide) containing 2-(4-aminophenyl)-5-aminobenzimidazole.

3. The preparation method according to claim 1, characterized in that, In Step 1, in the dimethylacetamide solution of graphene oxide, the mass fraction of graphene oxide is 4. The preparation method according to claim 1, characterized in that, In step 4, washing with water is carried out using deionized water at 70 °C.

5. High-strength and high-toughness heterocyclic aramid fiber prepared by the method according to claim 1.

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