A sizing method for graphene fibers

Abstract

This invention belongs to the field of fiber sizing technology and discloses a method for sizing graphene fibers. The method involves first pre-wetting the graphene fibers with a carbonate solvent, then immersing the graphene fibers in an electrophoretic coating solution. A uniform, dense, and firmly bonded polyether-type polyurethane coating is electrophoretically deposited on both the surface and interior of the graphene fibers. This invention employs a pre-wetting followed by electrophoretic deposition technique to sizing graphene fibers, ensuring uniform penetration of the sizing agent and avoiding localized dry areas or weak interfaces caused by insufficient wetting. This guarantees the uniformity of stress transfer in the final graphene fiber and forms a uniform coating on the graphene fiber surface.

Description

Technical Field

[0001] This invention belongs to the field of fiber sizing technology and relates to a sizing method for graphene fibers. Background Technology

[0002] Sizing is a crucial step in the fiber-to-fabric process, serving three main purposes: protecting the fiber surface, optimizing weaving performance, and improving interfacial properties. By forming a uniform coating layer on the monofilament surface, sizing effectively reduces frictional damage during subsequent weaving and warping processes, significantly improving fiber cohesion and abrasion resistance. Simultaneously, the binding effect of the sizing prevents fiber dispersion, enhancing weaving efficiency and fabric quality.

[0003] However, traditional sizing processes face significant challenges for graphene fibers (typically multifilaments). The surface of graphene fibers is primarily composed of sp... 2 Composed of hybrid carbon atoms, graphene fibers exhibit high chemical stability, characterized by low surface energy and high hydrophobicity. This inherent "inertness" makes it difficult for them to form good wetting and spreading with conventional sizing agents. Sizing droplets tend to aggregate into beads rather than spread uniformly on the fiber surface, resulting in a small interfacial contact area and weak physical adsorption. Unlike traditional glass or carbon fibers, the wrinkled surface of graphene fibers creates gaps after bundling. Traditional sizing agents rely solely on physical adsorption and simple mechanical anchoring, leading to poor bonding between graphene fiber bundles prepared by traditional sizing processes, making them prone to detachment.

[0004] Patent application CN119859379A discloses a high thermal conductivity graphene fiber and resin composite material, comprising continuous graphene fiber filaments coated with a sizing agent. The sizing process involves placing a completely dried graphene fiber bundle in a sizing tank containing sizing agents, ensuring the sizing agent completely submerges the fiber bundle, and then extruding excess sizing agent through upper and lower extrusion rollers at a speed of 0.05 m / s. The sized graphene fibers are then completely dried at room temperature. However, due to the surface inertness of graphene fibers, uneven wettability occurs during sizing, making uniform sizing difficult.

[0005] Patent application CN119980598A discloses an aramid fiber sizing device and method. After unwinding, the fiber is sizing in a sizing tank and then sent to a spreading and drying device for wet spreading, reducing mechanical damage to the fiber bundle and minimizing fuzz formation. Secondary spreading of the fiber bundle is achieved under high-frequency vibration of a vibrating roller, ensuring good monofilament dispersion. However, the excess sizing solution removed by vibration and the potentially generated extremely short fuzz may accumulate within the device, forming a source of contamination and posing a risk of re-adhering to the fiber surface.

[0006] Existing technology explores a simple method for preparing carbon nanotube / carbon fiber hybrid fibers. Electrophoretic deposition is performed in an acid-treated carbon nanotube / N,N-dimethylformamide suspension. A ring electrode ensures effective electrophoretic deposition, and sizing is carried out after electrophoretic deposition using a thermoplastic sizing agent. The carbon nanotubes are deposited on the carbon fiber surface and tightly adhered to it. The polymer matrix significantly improves the wettability and interfacial shear strength of the hybrid fibers. However, this technology essentially reinforces carbon fibers with carbon nanotubes, and the sizing technique still employs traditional sizing methods.

[0007] Patent CN118223209B discloses a glass fiber sizing device, including a conveyor belt for transporting glass fibers. Above the conveyor belt are a sizing frame and rollers for coating the glass fibers with sizing. The rollers can apply a clamping force to the glass fibers from multiple angles. The height of the rollers is adjustable, and the thickness of the sizing on the rollers changes accordingly with the height adjustment, thereby enabling the rollers to control the sizing thickness on the rollers while sizing glass fibers of different thicknesses. However, this device relies on the rollers directly picking up the sizing from the sizing frame, which cannot guarantee the uniformity of sizing.

[0008] In summary, due to the wrinkles on the surface of graphene filaments, large gaps are formed between the fibers. Traditional fiber sizing techniques are prone to uneven sizing of the filaments, resulting in uneven stress distribution. This leads to stress concentration during stretching and makes it difficult to achieve ideal mechanical properties.

[0009] Therefore, a sizing method for graphene fibers is needed to solve the above problems, so that a uniform and complete coating can be formed on the surface of the graphene fibers during the sizing process, thereby improving their tensile strength and wear resistance. Summary of the Invention

[0010] The purpose of this invention is to solve the problems existing in the prior art and to provide a sizing method for graphene fibers.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] A sizing method for graphene fibers involves first pre-impregnating the graphene fibers with a carbonate solvent, then immersing the graphene fibers in an electrophoretic solution to electrophoretically deposit a uniform, dense, and firmly bonded polyether polyurethane (PEU) coating on the surface and inside of the graphene fibers.

[0013] This invention employs a pre-impregnation and electrophoretic deposition technique to sizing graphene fibers.

[0014] During pre-impregnation, graphene fibers are immersed in carbonate solvents. The polar groups of the carbonate solvent can increase the surface energy of the graphene fibers and increase their polarity. This results in stronger polar-polar interactions and hydrogen bonds with the sizing agent in the subsequent process. Furthermore, due to its similarity and miscibility with the sizing agent, it can also improve the wetting and spreading of the sizing agent, laying the foundation for the subsequent electrophoretic deposition of the sizing agent on the surface of the graphene monofilament. This allows the sizing agent to penetrate evenly, avoiding local dry areas or weak interfaces caused by insufficient impregnation, and ensuring the uniformity of stress transfer in the final graphene fiber.

[0015] During electrophoretic deposition, under the influence of an electric field, the Coulomb force on the charged sizing agent particles drives them to move along the electric field lines. This active driving force rapidly penetrates into the microscopic wrinkles and grooves of the graphene fibers themselves. Traditional sizing methods rely on capillary action and surface tension of the solution for penetration, which is unsuitable for graphene fibers with inert surfaces and numerous wrinkles. The electric field force of electrophoretic deposition effectively overcomes these physical resistances, forming a uniform coating on the surface of the graphene fibers.

[0016] As a preferred technical solution:

[0017] The graphene fiber sizing method described above uses a carbonate solvent selected from one or more of propylene carbonate, dimethyl carbonate, and diethyl carbonate. The surface tension of the carbonate solvent used in this invention is similar to that of the subsequent electrophoresis solution, serving as a "transition phase." Pre-saturating the fiber surface with this solvent effectively reduces the interfacial tension between the fiber and the electrophoresis solution. Furthermore, it improves the wettability of the fiber surface to the subsequent electrophoresis solution and reduces interfacial impedance.

[0018] The sizing method for graphene fibers described above involves a pre-impregnation temperature of 25-35°C and a time of 10-15 minutes.

[0019] In the above-described method for sizing graphene fibers, the electrophoretic solution is a mixture of an aqueous solution of polyether polyurethane and an aqueous solution of electrolyte. The polyether polyurethane is a cationic polyether polyurethane (such as quaternary ammonium salt modified polyether polyurethane or amino modified polyether polyurethane), and the graphene fibers are connected to the cathode during electrophoretic deposition. Alternatively, the polyether polyurethane can be anionic polyether polyurethane (such as carboxylate polyether polyurethane or sulfonate polyether polyurethane), and the graphene fibers are connected to the anode during electrophoretic deposition. The electrolyte is KCl or NaCl.

[0020] In the graphene fiber sizing method described above, the concentration of the polyether polyurethane aqueous solution is 0.5wt%-2wt%, the concentration of the electrolyte aqueous solution is 0.1-1.0M, and the mass ratio of the polyether polyurethane aqueous solution to the electrolyte aqueous solution is 4-20:1.

[0021] The sizing method for graphene fibers described above involves electrophoretic deposition at a voltage of 5-20V for 1-15 minutes.

[0022] In the above-described method for sizing graphene fibers, before pre-impregnation, the graphene fibers are acid-washed with an acid pickling solution to increase polar groups such as carboxyl groups (-COOH) and hydroxyl groups (-OH) on the surface of the graphene fibers, thereby improving hydrophilicity and slightly etching the surface to increase roughness.

[0023] The concentration of the pickling solution is 3wt%-10wt%, and the pickling solution is an aqueous solution of sulfuric acid or nitric acid. The pickling temperature is 30-40°C, and the pickling time is 30min-1h.

[0024] As described above, the graphene fiber sizing method further involves hot rolling after electrophoretic deposition to densify the fiber, eliminate structural defects, and make the stress distribution more uniform when the fiber is under load, thereby significantly improving its tensile strength and wear resistance. The hot rolling temperature is 100-140℃, the time is 2-5 min, the pressure is 5-15 MPa, and the roller gap is 100-500 μm.

[0025] The graphene fiber sizing method described above uses graphene fibers with specifications of 20-1000tex / 1000-50000F (i.e., the linear density of the graphene fiber is 20-1000tex, composed of 1000-50000 monofilaments). After sizing, the wear resistance of the graphene fiber is increased by 70%-85%, the tensile strength by 20%-35%, and the interfacial shear strength by 150%-200%. The improvement rate is calculated as (value after sizing - value before sizing) / value before sizing × 100%.

[0026] Beneficial effects:

[0027] (1) The present invention improves the surface energy of graphene fibers by using the polar groups of carbonate solvent, thereby increasing the degree of polarity. This results in stronger polar-polar interactions and hydrogen bonds with the sizing agent in the subsequent process. Furthermore, due to its similarity and compatibility with the sizing agent, it can also improve the wetting and spreading of the sizing agent, laying the foundation for the subsequent electrophoretic deposition of the sizing agent on the surface of the graphene monofilament. This allows the sizing agent to penetrate evenly, avoiding local dry areas or weak interfaces caused by insufficient wetting, and ensuring the uniformity of stress transmission in the final graphene fiber.

[0028] (2) The present invention uses the electric field effect during electrophoretic deposition to drive the charged sizing agent particles to move along the direction of the electric field lines by the Coulomb force. This allows the sizing agent to quickly penetrate into the micro-folds and grooves of the graphene fiber itself, and finally form a uniform coating on the surface of the graphene fiber. Attached Figure Description

[0029] Figure 1 This is a flowchart of the sizing process for the graphene fibers of the present invention.

[0030] Figure 2 This is a schematic diagram of the electrophoretic deposition of a polyether-type polyurethane coating on the surface and inside of graphene fibers according to the present invention.

[0031] Among them, 11-solution tank A, 12-solution tank B, 2-roller, 3-pre-impregnated graphene fiber, 4-electrophoretic deposition device, 5-hot roller, 6-winding shaft, 7-charged sizing agent particles, 8-ions with opposite charges, 9-pair electrodes. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0033] To ensure that the performance of the substances used in each embodiment and comparative example is fully disclosed, the manufacturers and brands of the substances are specified. Other manufacturers and brands that conform to the limitations of this invention are also feasible.

[0034] The test methods for the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0035] Tensile strength: Tested according to GB / T 3362-2017 "Test Method for Tensile Properties of Carbon Fiber Multifilament" (the adhesive used in the test was prepared according to A.3.3 of the standard).

[0036] Abrasion life: Tested according to ASTM D3108-2001, "Standard test method for coefficient of friction between yarn and solid material".

[0037] Interfacial shear strength: The microdroplet debonding method was used for determination. Single fibers were randomly selected from graphene fibers before and after sizing, and fixed flat on a U-shaped paper frame. A resin mixture was prepared with E-51 epoxy resin (epoxy value 0.51) and curing agent (m-phenylenediamine, CAS No.: 108-45-2) at a mass ratio of 100:14. The resin mixture was then drop-coated onto the surface of the single fiber using a micro-syringe, forming independent microdroplets (each droplet volume controlled at 0.1-0.5 μL) encapsulating the fiber. The fiber sample with the microdroplets was placed in an oven and cured at 80℃ for 2 hours, followed by 120℃ for 2 hours. Using a composite material interface evaluation instrument, under microscope assistance, the microdroplets were clamped onto a specially designed micro-blade or clamp, and the fiber was stretched axially at a constant rate of 0.05 mm / min until the microdroplets detached (peeled) from the fiber surface. The maximum load F at the moment of microdroplet debonding was recorded. max (Unit: N), and the effective embedding length L (unit: mm) of the microdroplet and fiber and the fiber diameter D (unit: mm) were measured using a microscope, and the interfacial shear strength (IFSS, unit: MPa) was calculated: IFSS = F max / (π•D•L).

[0038] Example 1

[0039] A sizing method for graphene fibers, the sizing process is as follows: Figure 1 As shown, the steps are as follows:

[0040] (1) Pretreatment;

[0041] Graphene fibers (200 tex / 10000 F, untwisted, wear life of 5500 cycles, tensile strength of 420 MPa, interfacial shear strength of 10 MPa) were ultrasonicated at 30°C for 30 min in solution tank A 11 containing a 3 wt% sulfuric acid aqueous solution.

[0042] (2) Preparation of electrophoresis solution;

[0043] First, cationic polyether polyurethane (manufacturer: Shanghai Bolino New Material Technology Co., Ltd., brand name: PU-104) and deionized water are mixed evenly to obtain a polyether polyurethane aqueous solution with a concentration of 0.5wt%. Then, KCl and deionized water are mixed evenly to obtain a KCl aqueous solution with a concentration of 0.1M. Finally, the polyether polyurethane aqueous solution and KCl aqueous solution are mixed evenly at a mass ratio of 4:1 to obtain the electrophoresis solution.

[0044] (3) After the graphene fibers treated in step (1) are rolled on a spool 2, they are pre-wetted in a solution tank B 12 containing propylene carbonate at 25°C for 10 min. Then, after the graphene fibers are rolled on a spool 2, the pre-wetted graphene fibers 3 are immersed in the electrophoretic solution prepared in step (2) using an electrophoretic deposition device 4. A polyether-type polyurethane coating is electrophoretically deposited on the surface and inside of the graphene fibers. The voltage of the electrophoretic deposition is 5V and the time is 15 min. The graphene fibers are connected to the cathode during the electrophoretic deposition.

[0045] (4) Under the conditions of 100℃ and 5MPa, the graphene fiber after electrophoretic deposition is hot-rolled by hot roller 5 for 5min and then wound by take-up shaft 6; wherein the gap between the hot rollers is 500μm.

[0046] After sizing, the wear resistance of graphene fibers increased by 70%, tensile strength by 20%, and interfacial shear strength by 150%.

[0047] Comparative Example 1

[0048] A sizing method for graphene fibers is basically the same as in Example 1, except that: in step (3), pre-impregnation is no longer performed, but the graphene fibers treated in step (1) are directly electrophoretically deposited.

[0049] After sizing, the wear resistance of graphene fibers increased by 50%, tensile strength by 10%, and interfacial shear strength by 80%.

[0050] Comparing Comparative Example 1 and Example 1, it can be seen that the improvement rates of wear resistance, tensile strength, and interfacial shear strength of the graphene fibers after sizing in this comparative example are reduced. This is because the polar groups of the carbonate solvent used in Example 1 during pre-wetting can increase the surface energy of the graphene fibers and increase the degree of polarity. This results in stronger polar-polar interactions and hydrogen bonds with the sizing agent in the subsequent process. Furthermore, due to its similarity and miscibility with the sizing agent, it can also improve the wetting and spreading of the sizing agent, laying the foundation for the subsequent electrophoretic deposition of the sizing agent on the surface of the graphene monofilament. This allows the sizing agent to penetrate evenly, avoiding local dry areas or weak interfaces caused by insufficient wetting, and ensuring the uniformity of stress transmission in the final graphene fiber.

[0051] Comparative Example 2

[0052] A sizing method for graphene fibers is basically the same as in Example 1, except that step (2) is omitted and in step (3), the graphene fibers treated in step (1) are directly impregnated in a sizing agent (manufacturer: Covestro AG, brand name: Baybond® PU 272); wherein the impregnation temperature is 25°C and the impregnation time is 30 min.

[0053] After sizing, the wear resistance of graphene fibers increased by 20%, tensile strength by 5%, and interfacial shear strength by 50%.

[0054] Comparing Comparative Example 2 and Example 1, it can be seen that the wear life, tensile strength and interfacial shear strength of the graphene fiber after sizing in this comparative example are only slightly improved. This is because the surface inertness of graphene fiber makes it unevenly contacted when directly immersed in sizing agent. The sizing agent cannot directly contact the interior of graphene fiber, resulting in uneven stress and no significant improvement in mechanical properties.

[0055] Example 2

[0056] A method for sizing graphene fibers, comprising the following steps:

[0057] (1) Pretreatment;

[0058] Graphene fibers (600tex / 30000F, untwisted, with a wear life of 7500 cycles, tensile strength of 500MPa, and interfacial shear strength of 15MPa) were ultrasonicated at 35°C for 50 minutes in solution tank A containing a 5wt% nitric acid aqueous solution.

[0059] (2) Preparation of electrophoresis solution;

[0060] First, cationic polyether polyurethane (manufacturer: BASF, Germany, brand name: Elastollan® 1185 A10) and deionized water were mixed evenly to obtain a polyether polyurethane aqueous solution with a concentration of 1.1 wt%. Then, NaCl and deionized water were mixed evenly to obtain a NaCl aqueous solution with a concentration of 0.5 M. Finally, the polyether polyurethane aqueous solution and the NaCl aqueous solution were mixed evenly at a mass ratio of 12:1 to obtain the electrophoresis solution.

[0061] (3) The graphene fibers treated in step (1) are pre-wetted in solution tank B containing dimethyl carbonate at 30°C for 12 min. Then, the pre-wetted graphene fibers are immersed in the electrophoretic solution prepared in step (2) using an electrophoretic deposition device. A polyether-type polyurethane coating is electrophoretically deposited on the surface and inside of the graphene fibers. The voltage of the electrophoretic deposition is 10V and the time is 9 min. The graphene fibers are connected to the cathode during the electrophoretic deposition.

[0062] (4) Under the conditions of 120℃ and 10MPa, the graphene fibers after electrophoretic deposition are hot-rolled for 3 minutes and then wound up through a take-up shaft; wherein the gap between the hot rollers is 230μm.

[0063] After sizing, the wear resistance of graphene fibers increased by 76%, tensile strength by 22%, and interfacial shear strength by 163%.

[0064] Example 3

[0065] A method for sizing graphene fibers, comprising the following steps:

[0066] (1) Pretreatment;

[0067] Graphene fibers (specifications: 1000tex / 50000F, untwisted, abrasion life: 40500 cycles, tensile strength: 630MPa, interfacial shear strength: 18MPa) were ultrasonicated at 40°C for 60 minutes in solution tank A containing a 10wt% sulfuric acid aqueous solution.

[0068] (2) Preparation of electrophoresis solution;

[0069] First, anionic polyether polyurethane (manufacturer: Covestro AG, brand name: Impranil® DLU) and deionized water are mixed evenly to obtain a polyether polyurethane aqueous solution with a concentration of 2wt%. Then, NaCl and deionized water are mixed evenly to obtain a NaCl aqueous solution with a concentration of 1M. Finally, the polyether polyurethane aqueous solution and the NaCl aqueous solution are mixed evenly at a mass ratio of 20:1 to obtain the electrophoresis solution.

[0070] (3) The graphene fibers treated in step (1) are pre-wetted in solution tank B containing diethyl carbonate at 35°C for 15 min. Then, the pre-wetted graphene fibers are immersed in the electrophoretic deposition solution prepared in step (2) using an electrophoretic deposition device. A polyether-type polyurethane coating is electrophoretically deposited on the surface and inside of the graphene fibers, such as... Figure 2 As shown, during the deposition process, the counter electrode 9 is connected to the cathode, and the pre-wetted graphene fiber 3 is connected to the anode. The Coulomb force on the charged sizing agent particles 7 will drive them to move along the direction of the electric field lines, and the ions 8 with opposite charges will move towards the counter electrode 9. The electrophoretic deposition voltage is 20V and the time is 1min.

[0071] (4) Under the conditions of 140℃ and 15MPa, the graphene fiber after electrophoretic deposition is hot-rolled for 2 minutes and then wound up through a take-up shaft; wherein the gap between the hot rollers is 100μm.

[0072] After sizing, the wear life of graphene fibers increased by 74%, the tensile strength increased by 26%, and the interfacial shear strength increased by 175%.

[0073] Example 4

[0074] A method for sizing graphene fibers, comprising the following steps:

[0075] (1) Pretreatment;

[0076] Graphene fibers (specification 20tex / 1000F, untwisted, wear resistance life of 65,000 cycles, tensile strength of 710MPa, interfacial shear strength of 17MPa) were ultrasonicated at 35°C for 40 minutes in solution tank A containing a 5wt% sulfuric acid aqueous solution.

[0077] (2) Preparation of electrophoresis solution;

[0078] First, anionic polyether polyurethane (manufacturer: Covestro AG, brand name: Impranil® DLU) and deionized water are mixed evenly to obtain a 1 wt% polyether polyurethane aqueous solution. Then, NaCl and deionized water are mixed evenly to obtain a 0.8 M NaCl aqueous solution. Finally, the polyether polyurethane aqueous solution and the NaCl aqueous solution are mixed evenly at a mass ratio of 15:1 to obtain the electrophoresis solution.

[0079] (3) The graphene fibers treated in step (1) are pre-wetted in solution tank B containing carbonate solvent (composed of methyl carbonate and dimethyl carbonate in a mass ratio of 1:1) at 28°C for 13 min. Then, the pre-wetted graphene fibers are immersed in the electrophoretic solution prepared in step (2) using an electrophoretic deposition device to electrophoretically deposit a polyether-type polyurethane coating on the surface and inside of the graphene fibers. The voltage of electrophoretic deposition is 15V and the time is 6 min. The graphene fibers are connected to the anode during electrophoretic deposition.

[0080] (4) Under the conditions of 135℃ and 13MPa, the graphene fibers after electrophoretic deposition are hot-rolled for 3 minutes and then wound up through a take-up shaft; wherein the gap between the hot rollers is 300μm.

[0081] After sizing, the wear resistance of graphene fibers increased by 81%, tensile strength by 25%, and interfacial shear strength by 186%.

[0082] Example 5

[0083] A method for sizing graphene fibers, comprising the following steps:

[0084] (1) Pretreatment;

[0085] Graphene fibers (specifications: 100tex / 5000F, untwisted, wear resistance: 85,500 cycles, tensile strength: 750 MPa, interfacial shear strength: 20 MPa) were ultrasonicated at 40°C for 30 min in solution tank A containing a 10 wt% nitric acid aqueous solution.

[0086] (2) Preparation of electrophoresis solution;

[0087] First, cationic polyether polyurethane (manufacturer: Shanghai Bolino New Material Technology Co., Ltd., brand name: PU-104) and deionized water are mixed evenly to obtain a polyether polyurethane aqueous solution with a concentration of 1.5wt%. Then, KCl and deionized water are mixed evenly to obtain a KCl aqueous solution with a concentration of 0.7M. Finally, the polyether polyurethane aqueous solution and the KCl aqueous solution are mixed evenly at a mass ratio of 18:1 to obtain the electrophoresis solution.

[0088] (3) The graphene fibers treated in step (1) are pre-wetted in solution tank B containing carbonate solvent (composed of diethyl carbonate and dimethyl carbonate in a mass ratio of 1:1) at 33°C for 12 min. Then, the pre-wetted graphene fibers are immersed in the electrophoretic solution prepared in step (2) using an electrophoretic deposition device to electrophoretically deposit a polyether-type polyurethane coating on the surface and inside of the graphene fibers. The voltage of electrophoretic deposition is 18V and the time is 9 min. The graphene fibers are connected to the cathode during electrophoretic deposition.

[0089] (4) Under the conditions of 130℃ and 14MPa, the graphene fibers after electrophoretic deposition are hot-rolled for 4 minutes and then wound up through a take-up shaft; wherein the gap between the hot rollers is 410μm.

[0090] After sizing, the wear resistance of graphene fibers increased by 85%, tensile strength by 35%, and interfacial shear strength by 200%.

Claims

1. A method for sizing graphene fibers, characterized in that, First, graphene fibers are pre-impregnated with carbonate solvents, and then the graphene fibers are immersed in an electrophoretic solution to electrophoretically deposit a polyether-type polyurethane coating on the surface and inside of the graphene fibers. The carbonate solvent is one or more of propylene carbonate, dimethyl carbonate, and diethyl carbonate; The electrophoresis solution is a mixture of a polyether polyurethane aqueous solution and an electrolyte aqueous solution. The polyether polyurethane is cationic polyether polyurethane, and graphene fibers are connected to the cathode during electrophoretic deposition. Alternatively, the polyether polyurethane is anionic polyether polyurethane, and graphene fibers are connected to the anode during electrophoretic deposition. The electrolyte is KCl or NaCl.

2. The sizing method for graphene fibers according to claim 1, characterized in that, The pre-impregnation temperature is 25-35°C, and the time is 10-15 minutes.

3. The sizing method for graphene fibers according to claim 1, characterized in that, The concentration of the polyether polyurethane aqueous solution is 0.5wt%-2wt%, the concentration of the electrolyte aqueous solution is 0.1-1.0M, and the mass ratio of the polyether polyurethane aqueous solution to the electrolyte aqueous solution is 4-20:

1.

4. The sizing method for graphene fibers according to claim 1, characterized in that, The electrophoretic deposition voltage is 5-20V, and the time is 1-15min.

5. The sizing method for graphene fibers according to claim 1, characterized in that, Before pre-impregnation, the graphene fibers are also pickled with an acid pickling solution. The concentration of the pickling solution is 3wt%-10wt%, and the pickling solution is an aqueous solution of sulfuric acid or nitric acid. The pickling temperature is 30-40°C, and the pickling time is 30min-1h.

6. The sizing method for graphene fibers according to claim 1, characterized in that, After electrophoretic deposition, the graphene fibers are subjected to hot rolling; the temperature of hot rolling is 100-140℃, the time is 2-5min, the pressure is 5-15MPa, and the roller gap is 100-500μm.

7. A method for sizing graphene fibers according to any one of claims 1 to 6, characterized in that, The specifications of graphene fiber are 20-1000tex / 1000-50000F; after sizing, the wear resistance life of graphene fiber is increased by 70%-85%, the tensile strength is increased by 20%-35%, and the interfacial shear strength is increased by 150%-200%.

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