Polyacrylonitrile-based carbon fiber as well as preparation method and application thereof

Abstract

The invention provides a preparation method of a polyacrylonitrile-based carbon fiber, and relates to the technical field of carbon fiber preparation, and the preparation method comprises the following steps: placing a polyacrylonitrile-based carbon fiber body as an anode in an electrolyte, and then carrying out surface treatment to obtain the polyacrylonitrile-based carbon fiber, wherein the conductivity of the electrolyte is 20 to 60 mS / cm; the charge quantity of the surface treatment is 5-10 C / g. By setting a low charge quantity and a low electrolyte concentration in the carbon fiber surface treatment process, a high surface treatment degree can be obtained, meanwhile, surface treatment functional groups are more uniform, polyacrylonitrile-based fibers with different performance indexes and different interface properties are prepared, and the application of hydrogen storage cylinders under different bursting pressure loads is met.

Description

Technical Field

[0001] This invention belongs to the technical field of carbon fiber preparation, specifically relating to a polyacrylonitrile-based carbon fiber, its preparation method, and its application. Background Technology

[0002] Carbon fiber is a high-performance reinforcing material with properties such as high strength, high modulus, high temperature resistance, wear resistance, corrosion resistance, electrical conductivity, and thermal conductivity. It also combines the flexibility and processability of fibers with the high tensile strength of carbon materials. In recent years, with the improvement of production technology and the expansion of production scale, carbon fiber has found applications in new textile machinery, carbon fiber composite core cables, wind turbine blades, carbon fiber composite bottles, oilfield drilling, medical devices, automotive components, building reinforcement materials, and sporting goods. Whether in the traditional aerospace field or in emerging markets such as automotive components and wind turbine blades, the application scope of carbon fiber is gradually expanding.

[0003] Improving the surface properties of carbon fiber is an important process in carbon fiber production, thereby enhancing the interfacial bonding performance between carbon fiber and the resin matrix to meet the requirements for use in carbon fiber composite bottles. Summary of the Invention

[0004] Therefore, the present invention provides a polyacrylonitrile-based carbon fiber, its preparation method and application, with the main objective of obtaining polyacrylonitrile-based carbon fiber with excellent interfacial bonding properties.

[0005] To address the aforementioned problems, this invention provides a method for preparing polyacrylonitrile-based carbon fibers, comprising the following steps: Polyacrylonitrile-based carbon fiber body is placed in an electrolyte as an anode and then subjected to surface treatment to obtain polyacrylonitrile-based carbon fiber. The electrolyte has a conductivity of 20-60 mS / cm; the surface treatment has a charge of 5-10 C / g.

[0006] Furthermore, the electrolyte is one of sulfuric acid, acetic acid, ammonium bicarbonate, and sodium hydroxide; and / or The temperature of the electrolyte is 15~35℃; and / or The voltage for the surface treatment is 15~36V.

[0007] Furthermore, the polyacrylonitrile-based carbon fiber body is prepared by the following method: Carbon fiber precursors were prepared using a dry-jet wet spinning process. The carbon fiber precursors were then subjected to pre-oxidation treatment, low-temperature carbonization treatment, and high-temperature carbonization treatment in sequence to obtain the polyacrylonitrile-based carbon fiber body.

[0008] Furthermore, the step of preparing carbon fiber precursor using the dry-jet wet spinning process includes: The raw materials are subjected to a polymerization reaction to obtain a spinning solution; the spinning solution is then subjected to dry zone stretching, coagulation bath curing and post-treatment in sequence to obtain the carbon fiber precursor. The raw materials include monomers and solvents; the monomers include acrylonitrile and itaconic acid; the solvent is dimethyl sulfoxide; preferably, in the monomers, the mass percentage of acrylonitrile is 98-99.5% and the mass percentage of itaconic acid is 0.5%-2.0%.

[0009] Furthermore, the intrinsic viscosity of the spinning solution is 1.7~2.0 l / g; the solid content of the spinning solution is 19.5~21.5%; and / or The stretching during the solidification treatment in the coagulation bath is 3.0%~5.0%; and / or The amount of oil adhering to the carbon fiber precursor is 0.6~2.5%.

[0010] Furthermore, the temperature of the pre-oxidation treatment is 220~270℃; and / or The pre-oxidation treatment applied a draw ratio of 0.85 to 0.90; and / or The density of the pre-oxidized fiber obtained after pre-oxidation treatment is 1.330~1.360 g / cm³. 3 .

[0011] Furthermore, the low-temperature carbonization treatment temperature is 400~800℃; and / or The high-temperature carbonization treatment temperature is 1100~1600℃; and / or The stretching ratio applied during high-temperature carbonization is 0.88 to 0.95.

[0012] Furthermore, the polyacrylonitrile-based carbon fiber body has a specification of 6k, 12k, or 24k.

[0013] On the other hand, the present invention provides a polyacrylonitrile-based carbon fiber, wherein the polyacrylonitrile-based carbon fiber is obtained by any of the preparation methods described above; the surface roughness of the polyacrylonitrile-based carbon fiber is 30~50nm.

[0014] In another aspect, the present invention provides an application of the above-mentioned polyacrylonitrile-based carbon fiber, wherein the polyacrylonitrile-based carbon fiber is used to prepare a test hydrogen storage cylinder; wherein the volume of the test hydrogen storage cylinder is 50~200L.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention achieves a high degree of surface treatment by setting a low charge amount (i.e., pulsed energizing) and a low electrolyte concentration during the carbon fiber preparation process, especially during the surface treatment process, while ensuring precise control of the electrolyte temperature and concentration. By implementing the above-mentioned methods, this invention obtains carbon fibers with a high degree of surface treatment and good interfacial properties, thereby achieving the beneficial effect of higher burst pressure resistance of hydrogen storage cylinders prepared using this type of polyacrylonitrile-based carbon fiber. Detailed Implementation

[0016] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific implementation methods, structures, features, and effects according to the present invention are described in detail below with reference to embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0017] On one hand, the present invention provides a method for preparing polyacrylonitrile-based carbon fiber, comprising the following steps: Polyacrylonitrile-based carbon fiber body is placed in an electrolyte as an anode and then subjected to surface treatment to obtain polyacrylonitrile-based carbon fiber. The electrolyte has a conductivity of 20-60 mS / cm; the surface treatment has a charge of 5-10 C / g.

[0018] Furthermore, the electrolyte is one of sulfuric acid, acetic acid, ammonium bicarbonate, and sodium hydroxide; and / or The temperature of the electrolyte is 15~35℃; and / or The voltage for the surface treatment is 15~36V.

[0019] Furthermore, the polyacrylonitrile-based carbon fiber body is prepared by the following method: Carbon fiber precursors were prepared using a dry-jet wet spinning process. The carbon fiber precursors were then subjected to pre-oxidation treatment, low-temperature carbonization treatment, and high-temperature carbonization treatment in sequence to obtain the polyacrylonitrile-based carbon fiber body.

[0020] Furthermore, the step of preparing carbon fiber precursor using the dry-jet wet spinning process includes: The raw materials are subjected to a polymerization reaction to obtain a spinning solution; the spinning solution is then subjected to dry zone stretching, coagulation bath curing and post-treatment in sequence to obtain the carbon fiber precursor. The raw materials include monomers and solvents; the monomers include acrylonitrile and itaconic acid; the solvent is dimethyl sulfoxide; preferably, in the monomers, the mass percentage of acrylonitrile is 98-99.5% and the mass percentage of itaconic acid is 0.5%-2.0%.

[0021] Furthermore, the intrinsic viscosity of the spinning solution is 1.7~2.0 l / g; the solid content of the spinning solution is 19.5~21.5%; and / or The stretching during the solidification treatment in the coagulation bath is 3.0%~5.0%; and / or The amount of oil adhering to the carbon fiber precursor is 0.6~2.5%.

[0022] Furthermore, the temperature of the pre-oxidation treatment is 220~270℃; and / or The pre-oxidation treatment applied a draw ratio of 0.85 to 0.90; and / or The density of the pre-oxidized fiber obtained after pre-oxidation treatment is 1.330~1.360 g / cm³. 3 .

[0023] Furthermore, the low-temperature carbonization treatment temperature is 400~800℃; and / or The high-temperature carbonization treatment temperature is 1100~1600℃; and / or The stretching ratio applied during high-temperature carbonization is 0.88 to 0.95.

[0024] Furthermore, the polyacrylonitrile-based carbon fiber body has a specification of 6k, 12k, or 24k.

[0025] On the other hand, the present invention provides a polyacrylonitrile-based carbon fiber, wherein the polyacrylonitrile-based carbon fiber is obtained by any of the preparation methods described above; the surface roughness of the polyacrylonitrile-based carbon fiber is 30~50nm.

[0026] By employing pulsed current treatment during the surface treatment process (when energized, hydroxide ions oxidize carbon atoms on the fiber surface, consuming hydroxide ions and reducing the surrounding hydroxide concentration; when de-energized, hydroxide ions diffuse towards the monofilaments in the center of the fiber bundle under the influence of the concentration difference until the next cycle, thus avoiding uneven oxidation of the monofilaments), the surface of the fiber is also prevented from being damaged by excessively large current.

[0027] The surface treatment effect of this application is good, mainly reflected in two aspects. On the one hand, the surface roughness of the fiber itself is relatively high (i.e., there are small grooves on the surface). On the other hand, the interface performance is good. A crucial indicator reflecting good interface performance is the high interlaminar shear strength of the fiber, which can reach more than 130 MPa. The interlaminar shear strength of the fiber after ordinary surface treatment is 100-110 MPa.

[0028] In another aspect, the present invention provides an application of the above-mentioned polyacrylonitrile-based carbon fiber, wherein the polyacrylonitrile-based carbon fiber is used to prepare a test hydrogen storage cylinder; wherein the volume of the test hydrogen storage cylinder is 50~200L.

[0029] The present invention will be further described below with reference to specific embodiments.

[0030] Example 1: This embodiment provides a method for preparing 12k dry-jet wet-spun carbon fibers with a single filament diameter of 7μm, including the following steps: Using dimethyl sulfoxide as a solvent, solution polymerization was employed with an acrylonitrile mass ratio of 98% and an itaconic acid mass ratio of 2.0%. This yielded a spinning solution with an intrinsic viscosity of 1.7 and a solid content of 21.0%. In the spinning solution, the coagulation bath draw was 4%, and the oiling agent adhesion during spinning was 2%. Oiling agent type A was used for the preparation of the precursor fiber. The precursor fiber was then oxidized in air at an oxidation temperature of 220–260°C with a draw ratio of -15%. The density of the oxidized fiber pre-oxidized body was 1.350 g / cm³. 3 When carbonizing the pre-oxidized fibers, the low-temperature carbonization temperature is 450~700℃, and the high-temperature carbonization temperature is 1100~1400℃; the applied carbonization draw ratio is -7.5%. Then, the high-temperature carbonized fibers are surface-treated by anodizing, wherein the electrolyte is a sulfuric acid solution, and the electrolyte temperature is 20℃. The electrical conductivity is 50 mS / cm. When the above-mentioned fibers pass through the surface treatment tank, the charge is 6 C / g. The surface treatment voltage is 25V, and the resulting carbon fiber surface roughness is 30 nm. The above-mentioned fibers are sized with an epoxy sizing agent with a sizing content of 0.9 wt%, and then dried at a constant temperature of 220℃ to prepare the above-mentioned fibers. The above-mentioned fibers are used to cover a gas cylinder with a volume of 80L. The carbon fiber wrapped around the gas cylinder can withstand a burst pressure of 90 MPa. Example 2: This embodiment provides a method for preparing dry-jet wet-spinning carbon fibers with a single filament diameter of 7μm and a diameter of 12k, including the following steps: Using dimethyl sulfoxide as a solvent, solution polymerization was employed with acrylonitrile mass ratio of 98.5% and itaconic acid mass ratio of 1.5%. This yielded a spinning solution with an intrinsic viscosity of 1.75 and a solid content of 20.5%. In the spinning solution, the coagulation bath draw was 5%, and the oiling agent adhesion during spinning was 1.5%. The spinning oiling agent used was type B, which was then used to prepare the precursor fiber. The precursor fiber was oxidized in air at an oxidation temperature of 220–260°C with a draw ratio of -13.5%, resulting in a pre-oxidized fiber density of 1.340 g / cm³. The pre-oxidized fiber was then carbonized at a low-temperature carbonization temperature of 40°C. The carbonization temperature ranges from 0 to 750℃, with a high-temperature carbonization temperature of 1200 to 1450℃. The applied carbonization draw ratio is -9.0%. The carbonized fibers are then surface-treated by anodizing, using a sulfuric acid solution at 20℃ with a conductivity of 40 mS / cm. The charge applied during surface treatment is 9.5 C / g, and the voltage used is 25V. The resulting carbon fiber surface roughness is 35 nm. The fibers are then sized with an epoxy sizing agent at a content of 1.0 wt%, and dried at a constant temperature of 210℃. The resulting fibers are then used to coat a gas cylinder with a volume of 80L. The carbon fibers wrapped around the gas cylinder can withstand a burst pressure of 100 MPa. Example 3: This embodiment provides a method for preparing dry-jet wet-spinning carbon fibers with a single filament diameter of 6μm and a diameter of 12k, including the following steps: Using dimethyl sulfoxide as a solvent, solution polymerization was employed with acrylonitrile mass ratio of 98.5% and itaconic acid mass ratio of 1.5%. This yielded a spinning solution with an intrinsic viscosity of 1.75 and a solid content of 20.5%. In the spinning solution, the coagulation bath draw was 5%, and the oiling agent adhesion during spinning was 1.8%. The spinning oiling agent used was type B, which was then used to prepare the precursor fiber. The precursor fiber was then oxidized in air at an oxidation temperature of 220–260°C with a draw ratio of -13.0%. The density of the oxidized fiber pre-oxidized material was 1.345 g / cm³. 3The pre-oxidized fibers were carbonized at low temperatures of 400-750°C and high temperatures of 1200-1450°C. The applied carbonization draw ratio was -10.0%. The high-temperature carbonized fibers were then surface-treated by anodizing, using a sulfuric acid solution at 25°C with a conductivity of 45 mS / cm. The fibers passed through a surface treatment tank with a charge of 9 C / g and a voltage of 25 V. The resulting carbon fiber surface roughness was 42 nm. The fibers were then sized with an epoxy sizing agent at a content of 1.1 wt% and dried at a constant temperature of 230°C to produce the fibers. These fibers were then used to coat a 90L gas cylinder, which could withstand a burst pressure of 95 MPa. Example 4: This embodiment provides a method for preparing dry-jet wet-spinning carbon fibers with a single filament diameter of 6μm and a diameter of 12k, including the following steps: Using dimethyl sulfoxide as a solvent, solution polymerization was employed with acrylonitrile mass ratio of 98.6% and itaconic acid mass ratio of 1.4%. This yielded a spinning solution with an intrinsic viscosity of 1.80 and a solid content of 20.5%. In the spinning solution, the coagulation bath draw was 4%, and the oiling agent adhesion during spinning was 1.7%. The spinning oiling agent used was oiling agent A, which was then used to prepare the precursor fiber. The precursor fiber was then oxidized in air at an oxidation temperature of 220–255°C with a draw ratio of -14.0%. The density of the oxidized fiber pre-oxidized material was 1.345 g / cm³. 3 The pre-oxidized fibers were carbonized at low temperatures of 400-700℃ and high temperatures of 1150-1450℃. The applied carbonization draw ratio was -8.5%. The high-temperature carbonized fibers were then surface-treated by anodizing, using a sulfuric acid solution at 25℃ with a conductivity of 50 mS / cm. The fibers passed through a surface treatment tank with a charge of 9.5 C / g and a voltage of 25V. The resulting carbon fiber surface roughness was 48 nm. The fibers were then sized with an epoxy sizing agent at a content of 1.1 wt% and dried at a constant temperature of 230℃ to produce the fibers. These fibers were then used to coat a 90L gas cylinder, which could withstand a burst pressure of 95 MPa. Example 5: This embodiment provides a method for preparing 12k dry-jet wet-spinning carbon fiber with a monofilament diameter of 5.5μm, including the following steps: Using dimethyl sulfoxide as a solvent, solution polymerization was employed with acrylonitrile mass ratio of 98.5% and itaconic acid mass ratio of 1.5%. This yielded a spinning solution with an intrinsic viscosity of 1.75 and a solid content of 20.5%. In the spinning solution, the coagulation bath draw was 5%, and the oiling agent adhesion during spinning was 1.5%. The spinning oiling agent used was type B, which was then used to prepare the precursor fiber. The precursor fiber was then oxidized in air at an oxidation temperature of 220–270°C with a draw ratio of -13.5%. The density of the oxidized fiber pre-oxidized material was 1.340 g / cm³. 3 The pre-oxidized fibers were carbonized at low temperatures of 400-750°C and high temperatures of 1200-1450°C. The applied carbonization draw ratio was -9.0%. The high-temperature carbonized fibers were then surface-treated by anodizing, using a sulfuric acid solution at 25°C with a conductivity of 50 mS / cm. The fibers passed through a surface treatment tank with a charge of 7 C / g and a voltage of 25 V. The resulting carbon fiber surface roughness was 40 nm. The fibers were then sized with an epoxy sizing agent at a content of 1.0 wt% and dried at a constant temperature of 220°C. The resulting fibers were then used to coat a 90 L gas cylinder. The carbon fibers wrapped around the gas cylinder were designed to withstand a burst pressure of 88 MPa. Example 6: This embodiment provides a method for preparing 12k dry-jet wet-spinning carbon fiber with a monofilament diameter of 5.5μm, including the following steps: Using dimethyl sulfoxide as a solvent, solution polymerization was employed with acrylonitrile mass ratio of 98.5% and itaconic acid mass ratio of 1.5%. This yielded a spinning solution with an intrinsic viscosity of 1.75 and a solid content of 20.5%. In the spinning solution, the coagulation bath draw was 4.8%, and the oiling agent adhesion during spinning was 1.5%. The spinning oiling agent used was type A, which was then used to prepare the precursor fiber. The precursor fiber was then oxidized in air at an oxidation temperature of 230–260°C with a draw ratio of -13.0%. The density of the oxidized fiber pre-oxidized body was 1.345 g / cm³. 3The pre-oxidized fibers were carbonized at low temperatures of 400-670°C and high temperatures of 1150-1450°C. The applied carbonization draw ratio was -10.5%. The high-temperature carbonized fibers were then surface-treated by anodizing, using a sulfuric acid solution at 20°C with a conductivity of 45 mS / cm. The fibers passed through a surface treatment tank with a charge of 8.5 C / g and a voltage of 25 V. The resulting carbon fiber surface roughness was 46 nm. The fibers were then sized with an epoxy sizing agent at a content of 0.8 wt% and dried at a constant temperature of 230°C to produce the fibers. These fibers were then used to coat a 90L gas cylinder, which could withstand a burst pressure of 105 MPa. Example 7: This embodiment provides a method for preparing dry-jet wet-spinning carbon fibers with a single filament diameter of 5μm and a diameter of 12k, including the following steps: Using dimethyl sulfoxide as a solvent, solution polymerization was employed with acrylonitrile mass ratio of 98.5% and itaconic acid mass ratio of 1.5%. This yielded a spinning solution with an intrinsic viscosity of 1.70 and a solid content of 20.0%. In the spinning solution, the coagulation bath draw was 4.9%, and the oiling agent adhesion during spinning was 1.2%. The spinning oiling agent used was oiling agent A, which was then used to prepare the precursor fiber. The precursor fiber was then oxidized in air at an oxidation temperature of 230–270°C with a draw ratio of -14.5%. The density of the oxidized fiber pre-oxidized material was 1.347 g / cm³. 3 The pre-oxidized fibers were carbonized at low temperatures of 400-700℃ and high temperatures of 1200-1400℃. The applied carbonization draw ratio was -7.5%. The high-temperature carbonized fibers were then surface-treated by anodizing, using a sulfuric acid solution at 20℃ with a conductivity of 40 mS / cm. The fibers passed through a surface treatment tank with a charge of 8 C / g and a voltage of 25 V. The resulting carbon fiber surface roughness was 37 nm. The fibers were then sized with an epoxy sizing agent at a content of 1.0 wt% and dried at a constant temperature of 220℃ to produce the fibers. These fibers were then used to coat a gas cylinder with a volume of 80 L. The carbon fibers wrapped around the gas cylinder were designed to withstand a burst pressure of 75 MPa. Example 8: This embodiment provides a method for preparing dry-jet wet-spinning carbon fibers with a monofilament diameter of 5μm and a diameter of 6k, including the following steps: Using dimethyl sulfoxide as a solvent, solution polymerization was employed with acrylonitrile mass ratio of 98.5% and itaconic acid mass ratio of 1.5%. This yielded a spinning solution with an intrinsic viscosity of 1.70 and a solid content of 20.0%. In the spinning solution, the coagulation bath draw was 4.0%, and the oiling agent adhesion during spinning was 1.8%. The spinning oiling agent used was type B, which was then used to prepare the precursor fiber. The precursor fiber was then oxidized in air at an oxidation temperature of 230–270°C with a draw ratio of -14.5%. The density of the oxidized fiber pre-oxidized material was 1.345 g / cm³. 3 The pre-oxidized fibers were carbonized at low temperatures of 400-750°C and high temperatures of 1200-1400°C. The applied carbonization draw ratio was -7.0%. The high-temperature carbonized fibers were then surface-treated by anodizing, using a sulfuric acid solution at 25°C with a conductivity of 50 mS / cm. The fibers passed through a surface treatment tank with a charge of 7.5 C / g and a voltage of 25 V. The resulting carbon fiber surface roughness was 40 nm. The fibers were then sized with an epoxy sizing agent at a content of 1.0 wt% and dried at a constant temperature of 210°C. The resulting fibers were then used to coat a gas cylinder with a volume of 80 L. The carbon fibers wrapped around the gas cylinder were designed to withstand a burst pressure of 100 MPa. Example 9: This embodiment provides a method for preparing dry-jet wet-spinning carbon fibers with a monofilament diameter of 5μm and a diameter of 24k, including the following steps: Using dimethyl sulfoxide as a solvent, solution polymerization was employed with an acrylonitrile mass ratio of 99.1% and an itaconic acid mass ratio of 0.9%. This yielded a spinning solution with an intrinsic viscosity of 1.80 and a solid content of 20.0%. In the spinning solution, the coagulation bath draw was 3.5%, and the oiling agent adhesion during spinning was 1.2%. The spinning oiling agent used was oiling agent A, which was then used to prepare the precursor fiber. The precursor fiber was then oxidized in air at an oxidation temperature of 220–255°C with a draw ratio of -14.0%. The density of the oxidized fiber pre-oxidized material was 1.335 g / cm³. 3The pre-oxidized fibers were carbonized at low temperatures of 380-760°C and high temperatures of 1250-1480°C. The applied carbonization draw ratio was -10.0%. The high-temperature carbonized fibers were then surface-treated by anodizing, using a sulfuric acid solution at 25°C with a conductivity of 40 mS / cm. The fibers passed through a surface treatment tank with a charge of 7.5 C / g and a voltage of 25 V. The resulting carbon fiber surface roughness was 42 nm. The fibers were then sized with an epoxy sizing agent at a content of 1.0 wt% and dried at a constant temperature of 230°C. The resulting fibers were then used to coat a gas cylinder with a volume of 80 L. The carbon fibers wrapped around the gas cylinder were designed to withstand a burst pressure of 87 MPa.

[0031] It will be readily understood by those skilled in the art that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0032] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A method for preparing polyacrylonitrile-based carbon fiber, characterized in that, Includes the following steps: Polyacrylonitrile-based carbon fiber body is placed in an electrolyte as an anode and then subjected to surface treatment to obtain polyacrylonitrile-based carbon fiber. The electrolyte has a conductivity of 20-60 mS / cm; the surface treatment has a charge of 5-10 C / g.

2. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that, The electrolyte is one of sulfuric acid, acetic acid, ammonium bicarbonate, and sodium hydroxide; and / or The temperature of the electrolyte is 15~35℃; and / or The voltage for the surface treatment is 15~36V.

3. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that, The polyacrylonitrile-based carbon fiber body was prepared by the following method: Carbon fiber precursors were prepared using a dry-jet wet spinning process. The carbon fiber precursors were then subjected to pre-oxidation treatment, low-temperature carbonization treatment, and high-temperature carbonization treatment in sequence to obtain the polyacrylonitrile-based carbon fiber body.

4. The method for preparing polyacrylonitrile-based carbon fiber according to claim 3, characterized in that, The steps for preparing carbon fiber precursor using the dry-jet wet spinning process include: The raw materials are subjected to a polymerization reaction to obtain a spinning solution; the spinning solution is then subjected to dry zone stretching, coagulation bath curing and post-treatment in sequence to obtain the carbon fiber precursor. The raw materials include monomers and solvents; the monomers include acrylonitrile and itaconic acid; the solvent is dimethyl sulfoxide; preferably, in the monomers, the mass percentage of acrylonitrile is 98-99.5% and the mass percentage of itaconic acid is 0.5%-2.0%.

5. The method for preparing polyacrylonitrile-based carbon fiber according to claim 4, characterized in that, The intrinsic viscosity of the spinning solution is 1.7~2.0 l / g; the solid content of the spinning solution is 19.5~21.5%; and / or The stretching during the solidification treatment in the coagulation bath is 3.0%~5.0%; and / or The amount of oil adhering to the carbon fiber precursor is 0.6~2.5%.

6. The method for preparing polyacrylonitrile-based carbon fiber according to claim 3, characterized in that, The temperature of the pre-oxidation treatment is 220~270℃; and / or The pre-oxidation treatment applied a draw ratio of 0.85 to 0.90; and / or The density of the pre-oxidized fiber obtained after pre-oxidation treatment is 1.330~1.360 g / cm³. 3 .

7. The method for preparing polyacrylonitrile-based carbon fiber according to claim 3, characterized in that, The temperature for low-temperature carbonization is 400~800℃; and / or The high-temperature carbonization treatment temperature is 1100~1600℃; and / or The stretching ratio applied during high-temperature carbonization is 0.88 to 0.

95.

8. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that, The polyacrylonitrile-based carbon fiber body has one of the following specifications: 6k, 12k, and 24k.

9. A polyacrylonitrile-based carbon fiber, characterized in that, The polyacrylonitrile-based carbon fiber is obtained by the preparation method according to any one of claims 1 to 8; the surface roughness of the polyacrylonitrile-based carbon fiber is 30 to 50 nm.

10. The application of the polyacrylonitrile-based carbon fiber according to claim 9, characterized in that, The polyacrylonitrile-based carbon fiber is used to prepare a test hydrogen storage cylinder; wherein, the volume of the test hydrogen storage cylinder is 50~200L.