Method for modifying surface of carbon-based material using hydrophilic polymer and carbon-based material modified thereby

Abstract

The present invention provides a surface modification method using a hydrophilic polymer to improve the surface hydrophilicity of a carbon-based material. The present invention provides a useful technique which is suitable for various industrial applications by greatly improving the surface hydrophilicity of a carbon-based material due to a simple and economical process, and can overcome the limitations of existing surface modification techniques. In addition, the carbon-based material modified by the method of the present invention has a water-drop contact angle, which is used as an important index indicating surface hydrophilicity, reduced by 80% or greater compared to before modification, and has an oxygen content increased by about 15% or greater, and thus can be widely used in industrial groups, such as hydrophilic materials and those facilitating adsorption and absorption.

Description

Method for modifying the surface of a carbon-based material using a hydrophilic polymer and a carbon-based material modified by the method

[0001] The present invention relates to a method for modifying the surface of a carbon-based material using a hydrophilic polymer and a carbon-based material modified by the method.

[0002] Carbon-based materials, graphene, and its derivatives have attracted significant attention in various industrial fields, including electronics, energy storage, high-performance composites, and biosensors, due to their outstanding electrical, mechanical, and thermal properties. Graphene possesses a unique two-dimensional structure, possessing high electrical conductivity and mechanical strength despite being only one atomic layer thick. These properties give graphene the potential to play a key role in next-generation electronic devices, batteries, and ultra-high-strength materials. Furthermore, graphene derivatives, whose structural and property modifications broaden their application potential, are a key focus of research and development.

[0003] In particular, graphene nanoplatelets are nano-sized thin plate-shaped particles with the characteristics of graphene. They are designed to be easy to mass-produce and apply while maintaining the unique electrical, thermal, and mechanical properties of graphene, and are being utilized in various industries.

[0004] However, these carbon-based materials are inherently hydrophobic, limiting their interaction with water. This hydrophobicity hinders their use in water-based applications, significantly limiting their potential for diverse industrial applications. For example, hydrophilicity is crucial in areas such as conductive inks in aqueous systems, water treatment technologies, and biosensors. Hydrophobic materials like graphene are inherently limited in these applications.

[0005] To address these issues, various research efforts are underway to modify the surface of graphene and its derivatives to enhance their interaction with water. Currently, surface modification techniques primarily include chemical treatment and plasma treatment. Chemical treatment involves introducing specific compounds to the surface of a material to increase hydrophilicity, and surface properties can be adjusted through various chemical reactions. However, these methods are complex, require multiple steps, and use expensive or toxic chemicals, which can negatively impact the environment. Plasma treatment uses plasma gas to apply energy to the surface of a material, altering its chemical structure. While this can be effective in enhancing hydrophilicity, it also has the drawbacks of being complex and requiring expensive equipment.

[0006] Therefore, there is an urgent need for a technology for surface modification of carbon-based materials that is simple, economical, and environmentally friendly.

[0007] [Prior Art Literature]

[0008] [Patent Document]

[0009] Patent Document 1: Korean Patent Publication No. 10-2022-0095749 (July 7, 2022)

[0010] The present invention is intended to solve the problems of the above-mentioned prior art, and, compared to the conventional carbon-based material surface modification method, it is possible to increase process efficiency by only including a step of separating a material of a specific particle size without the need for a separate investigation of an inert gas or the like, and to provide a carbon-based material surface modification method that enables mixing with various hydrophilic materials by forming a hydrophilic surface and internal pores to control hydrophilic properties.

[0011] More specifically, the present invention provides a method for modifying the surface of a carbon-based material, comprising the steps of: (a) mechanically treating a carbon raw material to produce a carbon-based material having a D50 of 4 µm to 10 µm when analyzed by a particle size analyzer; (b) mixing the produced carbon-based material with a hydrophilic polymer solution; and (c) stirring.

[0012] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the carbon-based material is at least one selected from the group consisting of graphene, oxidized graphene, non-oxidized graphene, and graphene nanoplatelets, or a mixture of at least one selected from the group consisting of graphene, oxidized graphene, non-oxidized graphene, and graphene nanoplatelets.

[0013] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the hydrophilic polymer contained in the hydrophilic polymer solution is at least one selected from the group consisting of polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyetherimide (PEI), and polyacrylic acid (PAA).

[0014] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the step (b) of mixing the manufactured carbon-based material into a hydrophilic polymer solution is performed by adding 3 to 30 parts by weight of the carbon-based material to 100 parts by weight of the hydrophilic polymer contained in the hydrophilic polymer solution.

[0015] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the stirring step (c) is performed by stirring at 200 rpm to 300 rpm at a temperature of 40°C to 80°C.

[0016] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the surface water droplet contact angle of the carbon-based material after modifying the carbon-based material is reduced by 50% to 85% based on the surface water droplet contact angle of the carbon-based material before modification.

[0017] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the method for modifying the surface of a carbon-based material increases the content of an oxygen element contained in the carbon-based material.

[0018] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the method for modifying the surface of a carbon-based material additionally includes a step of (d) washing and drying.

[0019] In addition, the present invention seeks to provide a carbon-based material modified by the above-described carbon-based material surface modification method.

[0020] In addition, the present invention aims to provide a modified carbon-based material, characterized in that the modified carbon-based material has a surface water droplet contact angle reduced by 50% to 85% based on the surface water droplet contact angle of the carbon-based material before modification.

[0021] In addition, the present invention aims to provide a modified carbon-based material, characterized in that the modified carbon-based material has a carbon:oxygen ratio of 60:40 to 80:20.

[0022] The present invention provides a method for modifying the surface of a carbon-based material and a carbon-based material modified by the method for modifying the surface of the carbon-based material to solve the above-mentioned problem.

[0023] More specifically, the present invention provides a method for surface modification of a carbon-based material, comprising the steps of: (a) mechanically treating a carbon raw material to produce a carbon-based material having a D50 of 4 µm to 10 µm when analyzed by a particle size analyzer; (b) mixing the produced carbon-based material with a hydrophilic polymer solution; and (c) stirring.

[0024] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the carbon-based material is at least one selected from the group consisting of graphene, oxidized graphene, non-oxidized graphene, and graphene nanoplatelets, or a mixture of at least one selected from the group consisting of graphene, oxidized graphene, non-oxidized graphene, and graphene nanoplatelets.

[0025] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the hydrophilic polymer contained in the hydrophilic polymer solution is at least one selected from the group consisting of polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyetherimide (PEI), and polyacrylic acid (PAA).

[0026] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the step (b) of mixing the manufactured carbon-based material into a hydrophilic polymer solution is performed by adding 3 to 30 parts by weight of the carbon-based material to 100 parts by weight of the hydrophilic polymer contained in the hydrophilic polymer solution.

[0027] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the stirring step (c) is performed by stirring at 200 rpm to 300 rpm at a temperature of 40°C to 80°C.

[0028] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the surface water droplet contact angle of the carbon-based material after modifying the carbon-based material is reduced by 50% to 85% based on the surface water droplet contact angle of the carbon-based material before modification.

[0029] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the method for modifying the surface of a carbon-based material increases the content of an oxygen element contained in the carbon-based material.

[0030] In addition, the present invention provides a method for modifying the surface of a carbon-based material, characterized in that the method for modifying the surface of a carbon-based material additionally includes a step of (d) washing and drying.

[0031] In addition, the present invention provides a carbon-based material modified by the above-described carbon-based material surface modification method.

[0032] In addition, the present invention provides a modified carbon-based material, characterized in that the modified carbon-based material has a surface water droplet contact angle reduced by 50% to 85% based on the surface water droplet contact angle of the carbon-based material before modification.

[0033] In addition, the present invention provides a modified carbon-based material, characterized in that the modified carbon-based material has a carbon:oxygen ratio of 60:40 to 80:20.

[0034] The method for modifying the surface of a carbon-based material according to the present invention can be performed with a simpler process and lower cost compared to the chemical treatment method, which is a conventional method for modifying the surface of a carbon-based material.

[0035] In addition, the carbon-based material modified according to the present invention has a surface water droplet contact angle that is reduced by 50% to 85% compared to the surface water droplet contact angle of the carbon-based material before modification, so not only is the affinity for water greatly improved, but the content of oxygen elements is increased, so that it can be applied in various fields.

[0036] The attached drawings are intended to explain the contents of the present invention in more detail to a person skilled in the art, and the technical idea of ​​the present invention is not limited thereto.

[0037] Figure 1 is a flowchart for a method for modifying carbon-based materials.

[0038] Figure 2 compares scanning electron microscope (SEM) images of a carbon-based material before and after modification according to one embodiment of the present invention.

[0039] FIG. 3 compares the results of energy dispersive X-ray spectroscopy (EDX) analysis showing the carbon:oxygen ratio of a carbon-based material before and after modification according to one embodiment of the present invention.

[0040] Figure 4 compares the results of surface water droplet contact angle measurements that can determine the hydrophilicity of a carbon-based material before and after modification according to one embodiment of the present invention.

[0041] Hereinafter, a method for modifying the surface of a carbon-based material according to the present invention and a carbon-based material modified by the method will be described in detail, but the method for modifying the surface of a carbon-based material and the carbon-based material modified by the method are not limited by the following description.

[0042] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the present invention, and the present invention is defined solely by the scope of the claims.

[0043] The terminology used herein is for the purpose of describing embodiments only and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the mentioned components. Like reference numerals refer to like components throughout the specification, and "and / or" includes each and any combination of one or more of the mentioned components. Although "first", "second", etc. are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from another. Therefore, it should be understood that a first component mentioned below may also be a second component within the technical spirit of the present invention.

[0044] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those skilled in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0045] Spatially relative terms such as "below," "beneath," "lower," "above," and "upper" can be used to easily describe the relationship between one component and other components as depicted in the drawings. Spatially relative terms should be understood to include different orientations of the components during use or operation in addition to the orientations depicted in the drawings. For example, if a component depicted in the drawings were flipped over, a component described as "below" or "beneath" another component could end up "above" the other component. Thus, the exemplary term "below" can include both the above and below orientations. Components can also be oriented in other directions, and thus spatially relative terms can be interpreted accordingly.

[0046]

[0047] The present invention relates to a method for modifying the surface of a carbon-based material.

[0048] Specifically, the method for modifying a carbon-based material according to the present invention may include the steps of (a) mechanically treating a carbon raw material to produce a carbon-based material having a D50 of 4 µm to 10 µm when analyzed by a particle size analyzer; (b) mixing the produced carbon-based material with a hydrophilic polymer solution; and (c) stirring.

[0049] Here, "D50" analyzed by a particle size analyzer may mean a value corresponding to a cumulative percentage distribution of particles with a median particle size of 50%. In particular, in the experimental examples described later in this specification, measurements were made using a particle size analyzer (PSA) from Microtrac, and calculations were made using a Tri-laser system.

[0050]

[0051] Regarding the method for modifying the surface of a carbon-based material according to the present invention, each step is described in detail below.

[0052] A method for modifying the surface of a carbon-based material according to the present invention may include the step of (a) mechanically treating a carbon raw material to produce a carbon-based material having a D50 of 4 µm to 10 µm when analyzed with a particle size analyzer.

[0053] The above carbon raw material is not particularly limited, but may be one or more selected from the group consisting of graphene, oxidized graphene, non-oxidized graphene, and graphene nanoplatelets, or a mixture of one or more selected raw materials. Additionally, as the carbon raw material, one or a mixture of expandable graphite (EG), expanded graphite (EDG), or graphite oxide may be used, and in the case of graphene nanoplatelets (GNP, hereinafter the same), due to its excellent thermal conductivity, it is highly likely to be applied as a heat dissipation material, etc., and therefore, it is preferable to use GNP in the present invention.

[0054] The above mechanical treatment means a process of applying physical force to control the particle size, shape, surface area, and especially particle size in the present invention, of a material, and may use a method such as ball milling, ultrasonic treatment, dry milling, or rolling mill.

[0055] Specifically, in the present invention, as described below, dry milling was performed using an Air Jet Mill under conditions of 3 bar to 5 bar and 3000 rpm to 8000 rpm, but the present invention is not particularly limited thereto.

[0056] Analysis using the above particle size analyzer is to evaluate the size and distribution of powder or dispersed particles, and can be performed using methods such as laser diffraction analysis, dynamic light scattering (DLS), image analysis, sieve analysis, or sedimentation analysis.

[0057] Specifically, the present invention analyzes particle size by laser diffraction as described below, and in the case of a carbon-based material modified by the method for surface modification of a carbon-based material according to the present invention, the carbon-based material has a particle size of 4 µm to 15 µm, 4 µm to 10 µm, 4 µm to 8 µm, or 4 µm to 6 µm based on the D50 value, and in the case of a carbon-based material having a particle size within the above range, the reduction rate of the surface water droplet contact angle can be maximized, and thus, there is an effect of further increasing affinity with water.

[0058] The method for modifying the surface of a carbon-based material according to the present invention may include, after the step (a) described above, the step (b) of mixing the manufactured carbon-based material into a hydrophilic polymer solution.

[0059] The step of mixing the above-mentioned (b) manufactured carbon-based material into the hydrophilic polymer solution can be performed by adding 3 to 30 parts by weight, 5 to 20 parts by weight, and more preferably 8 to 15 parts by weight of the carbon-based material to 100 parts by weight of the hydrophilic polymer contained in the hydrophilic polymer solution.

[0060] When a hydrophilic polymer solution is used by adding a carbon-based material in the above range, the hydrophobic surface of the carbon-based material (GNP) is modified to be hydrophilic, and the modified surface has increased water permeability and spreadability on the surface, so there is an advantage in that it can contribute to the good performance of a heat-dissipating material utilizing the thermal conductivity of the carbon-based material (GNP) through the change in physical properties due to hydrophilic modification.

[0061] The hydrophilic polymer may be at least one selected from the group consisting of polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyetherimide (PEI), and polyacrylic acid (PAA), but is not particularly limited thereto. For example, the hydrophilic polymer may be replaced with a hydrophilic liquid in liquid form, and examples of the hydrophilic liquid include ethylene glycol, diethylene glycol, and hydroxy peroxide.

[0062] In particular, in the present invention, polyethylene glycol (PEG) was used as the hydrophilic polymer, and the reason for using polyethylene glycol (PEG) as the hydrophilic polymer is that, among hydrophilic polymers, polyethylene glycol (PEG) can exist in a liquid state, so it can easily bind to the surface of the carbonaceous raw material (GNP) and can easily penetrate between the lattice layers of the carbonaceous raw material (GNP), so that the surface of the carbonaceous raw material (GNP) can be modified even with a simple process. On the other hand, since hydrophilic polymers other than polyethylene glycol (PEG) are in powder form, it is difficult to proceed with the process for modifying the surface of the carbonaceous raw material (GNP) while it is dissolved in a solvent, and therefore, polyethylene glycol (PEG) is more suitable than other hydrophilic polymers. In addition, it is difficult to select an appropriate solvent that simultaneously dissolves hydrophilic polymers and carbonaceous raw materials (GNPs), and adding a solvent or another separate process may increase manufacturing costs and cause environmental pollution.

[0063] The method for modifying the surface of a carbon-based material according to the present invention may include a stirring step (c) after the step (b) described above.

[0064] The above stirring step is to mechanically stir or move the mixture to uniformly mix the materials within the mixture or to promote a specific reaction, and may use a method such as mechanical stirring, magnetic stirring, or ultrasonic stirring.

[0065] The above (c) stirring step can be performed, more specifically, by stirring at 200 rpm to 300 rpm at a temperature of 40°C to 80°C.

[0066] When stirring under the above temperature conditions and stirring speed, the hydrophilic polymer (PEG) can be penetrated and bound between the surface of the carbonaceous raw material (GNP) and the grid layers, thereby more efficiently modifying the hydrophobicity of the carbonaceous raw material (GNP) to hydrophilicity.

[0067] The method for modifying the surface of a carbon-based material according to the present invention can be performed such that the surface water droplet contact angle of the carbon-based material after modification is reduced by 50% to 85% based on the surface water droplet contact angle of the carbon-based material before modification.

[0068] In addition, the method for modifying the surface of a carbon-based material according to the present invention can increase the content of oxygen elements contained in the carbon-based material, and in this case, there is an effect of more efficiently modifying the hydrophobic surface of the carbon-based raw material (GNP) to be hydrophilic.

[0069] In the present invention, the method for modifying the carbon-based material may further include a washing and drying step (d) after the steps (a), (b), and (c) described above.

[0070] The above washing step is a step for removing unnecessary components or impurities after stirring, and can utilize methods such as filtration, centrifugation, washing, or extraction. Specifically, the present invention washes the stirred contents through a vacuum filtration method, and in this case, the loss of hydrophilic polymers (PEG) that penetrate and bind between the carbonaceous raw material (GNP) surface and the lattice layer is minimized, thereby maximizing the hydrophilic modification effect.

[0071] The above drying step is a step to remove moisture or solvent remaining on the surface or inside of the sample after washing, and may be performed using a method such as natural drying, hot air drying, vacuum drying, freeze drying, microwave drying, or infrared drying. Specifically, in the present invention, hot air drying is performed at a temperature of 100°C to 150°C, preferably at a temperature of 130°C, for 6 to 24 hours, preferably 12 hours. In this case, there is an effect of removing excess hydrophilic polymer (PEG), inducing a reaction between unreacted hydrophilic polymer (PEG) and carbonaceous raw material (GNP), and increasing the stability of the bond between the hydrophilic polymer (PEG) and carbonaceous raw material (GNP) after the reaction.

[0072] In addition, the method for modifying a carbon-based material according to the present invention may additionally include a step of bonding a hydrophilic polymer or the like to the surface of the carbon-based material.

[0073] Specifically, the stirring step may include a process in which a hydrophilic functional group of a hydrophilic polymer is introduced to the surface of the carbon-based material and to a depth (thickness) of 1 mm to 1 cm from the surface.

[0074] In this case, the stirring step may include a reaction between a hydrophobic chemical functional group, exemplified by a carbon-carbon single bond (CC), a carbon-carbon double bond (C=C), etc. contained on the surface of the carbon-based material, and a hydrophilic functional group (-OH, -COOH, -NH2, etc.) to be converted into a hydrophilic chemical functional group, exemplified by a carbon-oxygen single bond (CO, ether bond), a carbon-oxygen double bond (C=O, ester bond), etc.

[0075] In addition, the method for modifying a carbon-based material according to the present invention can form various oxidizing species containing O- (functional groups containing oxygen) on the surface of the carbon-based material by reacting with the hydrophilic polymer on the surface of the carbon-based material through stirring of the carbon-based material and the hydrophilic polymer solution.

[0076] In the present invention, the conversion of the chemical functional group and the change in the element content may be measured through FT-IR spectroscopy, energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction spectrum (XPS) analysis, etc., but in addition, the chemical functional group and the element content may be confirmed through various methods that can measure them, and the measurement method is not limited thereto.

[0077] Specifically, the surface carbon:oxygen ratio of the carbon-based material before and after the stirring step significantly changed, and more specifically, the oxygen content increased by 15% or more after the stirring step, so that the content of hydrophilic functional groups in the carbon-based material increased, thereby improving the properties of the hydrophilicity of the surface of the carbon-based material.

[0078] Additionally, the method for modifying a carbon-based material according to the present invention reduces the water droplet contact angle on the surface of the carbon-based material before and after the stirring step, and the water droplet contact angle on the surface of the carbon-based material before and after the stirring step can be reduced by 80% or more, so that it has the effect of modifying the hydrophobic properties of the surface of a carbon-based raw material (GNP) to hydrophilic properties and improving the hydrophilic properties.

[0079]

[0080] The present invention also relates to a carbon-based material modified by the aforementioned carbon-based material surface modification method.

[0081] Hereinafter, the above carbon-based material will be described in detail, but any content that overlaps with the content described in the method for modifying the surface of the carbon-based material described above will be omitted.

[0082] The above modified carbon-based material can have a surface water droplet contact angle reduced by 50% to 85% based on the surface water droplet contact angle of the carbon-based material before modification.

[0083] Additionally, the modified carbon-based material may have a carbon:oxygen ratio of 60:40 to 80:20.

[0084] As described above, in the case of a carbon-based material modified by the method for surface modification of a carbon-based material according to the present invention, since the surface water droplet contact angle reduction rate and the carbon:oxygen ratio are within the above-described range, not only is the affinity for water greatly improved, but the content of oxygen elements is increased, so that it can be applied in various fields.

[0085]

[0086] Hereinafter, the present invention will be described in more detail through specific manufacturing examples and examples. However, these manufacturing examples and examples are intended to exemplify the present invention, and the scope of the present invention is not limited to these manufacturing examples and examples.

[0087]

[0088] [Manufacturing example]

[0089] As shown in [Table 1] below, modified graphene nanoplatelets (GNP) samples were manufactured using the conditions of each example and comparative example.

[0090] Classification Preliminary Comparative Example 112345 Modification OXXXOO Weight of added GNP powder relative to 100 parts by weight of hydrophilic polymer solution 1021631733 Particle size of mixed GNP 5㎛3㎛5㎛16㎛3㎛16㎛

[0091] More specifically, graphite powder was prepared into graphene nano platelets (hereinafter referred to as GNPs) by particle size (3, 5, 16 μm) using an Air Jet Mill, and 2 to 33 parts by weight of GNP powder based on 100 parts by weight of polyethylene glycol (hereinafter referred to as PEG) was added differently according to each example and comparative example, and then stirred at 60°C for 1 hour at 200 to 300 rpm. Thereafter, the stirred mixture was washed and vacuum filtered to remove impurities, and dried with hot air at about 130°C for 12 hours to prepare each modified graphene nano platelet (GNP).

[0092]

[0093] [Experimental Example 1] Comparative observation of GNPs before and after modification using a scanning electron microscope (SEM).

[0094] After preparing modified GNP samples from each of the examples and comparative examples manufactured from the above manufacturing examples, the surface of the sample was scanned using an electron beam, and the signal emitted from the surface was detected to image the microstructure of the sample.

[0095] As a result, it was confirmed that the modification was properly performed as the surface structure of the carbon material after modification became more complex and rougher, with wrinkles and exposed layered structures, compared to before modification.

[0096] In particular, it was predicted that carbon-based materials modified with hydrophilic functional groups would have the effect of facilitating adsorption and absorption with hydrophilic materials by creating pores that facilitate moisture penetration and absorption.

[0097]

[0098] [Experimental Example 2] Comparative observation of GNP before and after modification using energy dispersive X-ray spectroscopy (EDX).

[0099] After preparing modified GNP samples of each example and comparative example manufactured from the above manufacturing examples, the characteristic X-rays generated when X-rays interact with specific atoms in the sample were analyzed to confirm which elements were present in the sample and how much of each element was included.

[0100] As a result, it was confirmed that the carbon:oxygen ratio of the surface of the carbon-based material after modification significantly changed compared to before modification, resulting in an increase in oxygen content. Specifically, it was confirmed that the oxygen atom content significantly increased compared to before modification through chemical bonding of hydrophilic functional groups on the GNP surface.

[0101] In particular, it was confirmed that the oxygen atom content before and after modification increased by approximately 15 times under the condition of a particle size of 5㎛, showing the greatest change.

[0102]

[0103] [Experimental Example 3] Comparison of water droplet contact angle measurements of GNPs before and after modification

[0104] After preparing modified GNP samples of each example and comparative example manufactured from the above manufacturing examples, the angle formed between the water droplet and the surface when the water droplet fell on the surface of the sample was measured. Generally, a larger contact angle corresponds to a hydrophobic surface, and a smaller contact angle corresponds to a hydrophilic surface.

[0105] As a result, the GNP surface before modification had an initial (0 second) angle of 80 degrees or more between the water droplet and the surface, and there was almost no difference in the contact angle between the initial (0 second) and later (3 seconds), whereas the GNP surface after modification had an initial (0 second) angle of 10 to 45 degrees, becoming more hydrophilic than before modification, and it was confirmed that the water droplet was absorbed into the GNP through the absence of a contact angle at the later (3 seconds) compared to the initial (0 second).

[0106] In particular, it was confirmed that not only was the initial (0 second) contact angle the lowest after modification under the condition of a particle size of 5㎛, but also the difference in contact angle change before and after modification was the greatest.

[0107]

[0108] [Experimental Results]

[0109] The results according to Experimental Examples 2 and 3 for the Examples and Comparative Examples are shown in [Table 2] below.

[0110] Classification Preliminary Comparison Example 112345 Carbon / Oxygen Ratio 2.80 44.87 57.14 39.65 2.25 3.12 Contact Angle Initial (0 sec) 13878 18644 23 Late (3 sec) 0878 18600

[0111] As can be confirmed in the above [Table 2], it can be seen that the carbon-based material (Example 1) modified according to the method of the present invention has improved hydrophilic properties according to the modification. In particular, in the case of a particle size of 5㎛, it was confirmed that the effect in modifying GNPs can be maximized through significant changes in the water droplet contact angle and oxygen content, unlike other particle sizes. In comparison, in the case of Comparative Example 2, it was confirmed that the effect in modifying GNPs was minimal because the carbon / oxygen ratio was high, slowing down the change in contact angle.

[0112]

[0113] The above description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single entity may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0114] The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. As a method for modifying the surface of carbon-based materials, (a) A step of manufacturing a carbon material having a D50 of 4㎛ to 10㎛ when analyzed with a particle size analyzer by mechanically treating a carbon raw material; (b) a step of mixing the manufactured carbon-based material into a hydrophilic polymer solution; and (c) A method for modifying the surface of a carbon-based material, comprising a stirring step.

2. In paragraph 1, A method for surface modification of a carbon-based material, characterized in that the carbon-based material is at least one selected from the group consisting of graphene, oxidized graphene, non-oxidized graphene, and graphene nanoplatelets, or a mixture of at least one selected from the group consisting of graphene, oxidized graphene, non-oxidized graphene, and graphene nanoplatelets.

3. In paragraph 1, A method for modifying the surface of a carbon-based material, characterized in that the hydrophilic polymer contained in the hydrophilic polymer solution is at least one selected from the group consisting of polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyetherimide (PEI), and polyacrylic acid (PAA).

4. In paragraph 1, A method for surface modification of a carbon-based material, characterized in that the step of mixing the manufactured carbon-based material into a hydrophilic polymer solution is performed by adding 3 to 30 parts by weight of the carbon-based material to 100 parts by weight of the hydrophilic polymer contained in the hydrophilic polymer solution.

5. In paragraph 1, A method for modifying the surface of a carbon-based material, characterized in that the stirring step (c) is performed by stirring at 200 rpm to 300 rpm at a temperature of 40°C to 80°C.

6. In paragraph 1, The method for modifying the surface of a carbon-based material is characterized in that, based on the surface water droplet contact angle of the carbon-based material before modification, the surface water droplet contact angle of the carbon-based material after modification is reduced by 50% to 85%.

7. In paragraph 1, The above method for modifying the surface of a carbon-based material is characterized by increasing the content of an oxygen element contained in the carbon-based material.

8. In paragraph 1, A method for modifying the surface of a carbon-based material, characterized in that it additionally includes a step of (d) washing and drying.

9. A carbon-based material modified by a carbon-based material surface modification method according to any one of clauses 1 to 8.

10. In paragraph 9, A modified carbon-based material, characterized in that the modified carbon-based material has a surface water droplet contact angle reduced by 50% to 85% based on the surface water droplet contact angle of the carbon-based material before modification.

11. In paragraph 9, The modified carbon-based material is characterized in that the carbon:oxygen ratio contained therein is 60:40 to 80:20.

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