Graphene film, graphene oxide film and their methods of manufacturing

Abstract

Multi-layer packaging comprising a plurality of layers of packaging materials, wherein one or more layers amongst the plurality of layers comprise a film comprising at least one of: graphene or graphe

Description

14 02 25 TECHNICAL FIELD 5 The present invention relates to graphene. In particular, though not exclusively, this invention relates to a graphene oxide film. The present invention also relates to a method of manufacturing a graphene oxide film. BACKGROUND io Graphene has been widely used for various applications in different industries. Owing to its unique physiochemical properties, the graphene has been increasingly used in biomedical devices, composites and coatings, electronic devices, sensors, membranes, packaging, or the similar. The properties may include, enhanced mechanical strength, 15 electrical conductivity, thermal conductivity, or the like. In packaging industry, the graphene may be used in a form of graphene oxide film with large surface area. Packaging is one of utmost importance in product's development. Apart from its primary role of containing, the packaging also protects products from physical, chemical, and biological 20 contamination. Therefore, it is almost impossible for a single layer structure to fulfil all the requirements. Therefore, multi-layer structures have been used which combine unique functionalities of several layers, possess superior properties as compared to the single layer structure in terms of mechanical properties, barrier properties and functional 25 properties. Therefore, there is an increasing demand for multi-layer structures for packaging, it is estimated that multi-layer structures account for 26% of packaging of market by weight. Conventionally, multi-layer structure may include barrier films made of metal foils, notably, a lamination of pure aluminium layer (99.5%) or its 14 02 25 alloy. However, there are certain problems associated with metal foils as they are considered environmentally unfriendly and / or may have high energy consumption during production. Often, adhesives or an adhesive layer are added between barrier films and other layers to ensure bonding 5 of various layers of the multi-layer structure. This may increase difficulties in recycling of the multi-layer structure. The recycling process of the multi-layer structures turned out to be challenging as identification, sorting and separation of various layers may be different. As a result, the multi-layer structure is sorted as a mixed plastic waste and subjected to io incineration. However, in an attempt to mitigate aforesaid problem of packaging, the graphene oxide film can be used as the barrier layer. However, the conventional graphene oxide film may be of poor quality in term of porosity, uniformity, and the like. For example, the conventional 15 graphene oxide may be highly porous resulting in permeability by fluids. Further, the conventional graphene oxide film has defects such as grain boundaries, point defects, or the similar. Hence, conventional graphene oxide films often exhibit less attractive barrier properties in packaging. The aforesaid limitations of the conventional graphene oxide film may be 20 due to processes involved in manufacturing of the same Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks associated with the graphene oxide film and their methods of manufacturing. SUMMARY OF THE INVENTION 25 A second aspect of the present invention provides a graphene oxide film comprising at least one layer of graphene oxide, wherein the graphene oxide film has a second thickness, and wherein the graphene oxide film is impermeable by fluids. In this regard, "layer of graphene oxide" refers to a structure formed by hexagonal rings of sp2 bonded carbon atoms and various oxygen containing functional groups. The carbon atoms are tightly packed into a two-dimensional honeycomb lattice in the at least one layer of graphene. 5 The functional groups may include epoxides, hydroxyl groups and carboxyl groups. The functional groups are present on surface of the two-dimensional honeycomb lattice. Optionally, the at least one layer of graphene oxide is substantially defect free. Optionally, absence of structural defects imparts impermeability to the graphene oxide film. In 10 one implementation, the graphene oxide film includes a number of layers of the graphene oxide. Optionally, the number of layers of the graphene oxide are densely packed with each other. Optionally, the number of layers of the graphene oxide has enhanced material homogeneity and interlayer binding, resulting in densely packed assembly of layers. is Optionally, a densely packed assembly of layers of the graphene oxide may impart enhanced impermeability to the graphene oxide film. Optionally, a number of layers of the graphene oxide in the graphene oxide film may impact the second thickness of the graphene oxide film. For example, a large number of layers of the graphene oxide, more is the 20 second thickness of the graphene oxide film. Optionally, the second thickness lies in a range of 0.5 pm to 20 pm. The second thickness lies in a range of 0.5 pm to 6 pm, 0.5 pm to 10 pm, 0.5 pm to 14 pm, 0.5 pm to 20 pm, 2 pm to 10 pm, 2 pm to 14 pm, 2 pm to 17 pm, 2 pm to 20 pm, 5 pm to 10 pm, 5 pm to 14 pm, 5 pm to 17 pm, 25 5 pm to 20 pm, 8 pm to 14 pm, 8 pm to 17 pm, 8 pm to 20 pm, 12 pm to 20 pm. optionally, the second thickness of the graphene oxide film depends upon volume of an exfoliated stabilized graphene oxide solution being passed through at least one second filter membrane as described in below paragraphs. Optionally, the graphene oxide film is used for 30 varying applications depending upon the second thickness of the graphene oxide film. For example, the graphene oxide film having the second thickness of 550 nm may be used as the barrier film in packaging. It will be appreciated that other applications of the graphene oxide film are well within the scope of the present invention. The graphene oxide film has enhanced flexibility, strength, high barrier 5 property, thermal stability and chemical stability. High impermeability of the graphene oxide film makes it suitable to be used for various application in different industries such as, food industry, medical industry, chemical industry, electronic industry, and the like. Optionally, the fluids include at least one of: gases, liquids. io Optionally, the graphene oxide film is incorporated as one or more layers within a multi-layer packaging, and wherein, when the multi-layer packaging is subjected to a recycling process, the graphene oxide film provides self-recyclable properties to the multi-layer packaging. In this LO regard, the multi-layer packaging may include three to twelve layers. CXI v is Optionally, the multi-layer packaging may be used as at least one of: a flexible packaging, a semi-rigid packaging. Examples of the flexible packaging may include, but are not limited to, sachets, packaging of soaps, packaging of personal hygiene products, packaging of condiments, packaging of medicines, health supplements, pouches, crisp bags. 20 Examples of the semi-rigid packaging may include food and beverage cartons. Optionally, the multi-layer packaging is made of polymer. The polymer could be selected from at least one of: Polyethylene (PE), Polydimethylsiloxane (PDMS), polyvinyl alcohol (PVA), Poly(methyl methacrylate) (PMMA), Polypropylene (PP), Polyhydroxyalkanoate (PHA), 25 Polybutylene succinate (PBS), Polylactic acid (PLA), Polybutylene terephthalate (PBT). Optionally, the graphene oxide film is incorporated by placing the graphene oxide film within layer(s) of the multi-layer packaging using at least one of: a robot, a machine with a robotic arm, hands of a person. Optionally, the graphene oxide film is incorporated by 30 a continuous process with layer(s) of the multi-layer packaging applied to its substrate using at least one of: roll-to-roll, adhesive lamination, thermal lamination, liquid lamination, additive manufacturing, three -dimensional (3D) printing. Owing to the presence of the oxygen containing functional groups on the at least one layer of the graphene oxide, the graphene oxide film forms a plurality of chemical bonds with 5 the polymer. The oxygen containing functional groups may be positively charged or negatively charged. Optionally, the positively charge and the negatively charged oxygen containing functional groups can electrostatically interact with the polymer. Optionally, the graphene oxide film is used as an additive within layers of the multi-layer packaging for 10 imparting enhanced mechanical, thermal, electrical properties to the multi-layer packaging. Optionally, the graphene oxide film is incorporated within the multi-layer packaging as an enhancement filler and / or compatibilizer. Advantageously, the technical effect of incorporating the graphene oxide film in the multi-layer packaging is that the during is recycling of the multi-layer packaging, the one or more layers of the graphene oxide film need not to be separated from the multi-layer packaging. The multi-layer packaging can be self-recycled with ease. A fourth aspect of the present invention provides a method of manufacturing a graphene oxide film, the method comprising: 20 - diluting graphite oxide paste in deionized (DI) water for obtaining a graphene oxide solution; sonicating the graphene oxide solution for a second time duration for preparing an exfoliated graphene oxide solution; and filtering the exfoliated graphene oxide solution for obtaining the 25 graphene oxide film of a second thickness on a third surface, and wherein the graphene oxide film comprises at least one layer of graphene oxide. In this regard, a required amount of the graphite oxide paste is mixed in a required amount of the DI water to dilute the graphite oxide paste. The required amount of the graphite oxide paste could lie in a range of 1 gm so to 20 gm. The required amount of the graphite oxide paste lies in a range of 1 gm to 5 gm, 1 gm to 10 gm, 1 gm to 15 gm, 1 gm to 18 gm, 1 gm to 20 gm, 4 gm to 10 gm, 4 gm to 15 gm, 4 gm to 18 gm, 4 gm to 20 gm, 8 gm to 15 gm, 8 gm to 18 gm, 8 gm to 20 gm, 13 gm to 18 gm, 13 gm to 20 gm. Optionally, the required amount of the DI water could lie in a range of 500 ml to 2000 ml. The required amount of the DI water 5 lies in a range of 500 ml to 900 ml, 500 ml to 1300 ml, 500 ml to 1700 ml, 500 ml to 2000 ml, 700 ml to 1300 ml, 700 ml to 1700 ml, 700 ml to 2000 ml, 1000 ml to 1300 ml, 1000 ml to 1700 ml, 1000 ml to 2000 ml, 1300 ml to 1700 ml, 1300 ml to 2000 ml. Optionally, a concentration of the graphene oxide solution lies in a range of 0.5 mg / ml to 2 mg / ml. io Optionally, the method further comprises synthesizing the graphite oxide paste from natural graphite. Optionally, the step of synthesizing the graphite oxide paste from the natural graphite is performed using a modified Hummer's method Optionally, in the modified Hummer's 1*0 method, 3 gm of graphite powder is pre-oxidized with 360 ml of C\J 15 concentrated sulfuric acid (H2SO4) along-with 90ml nitric acid (HNO3). A £\J mixture obtained in previous step is stirred in an ice bath for the time period of 4 hours to 16 hours. The time period lies in a range of 4 hours to 7 hours, 4 hours to 12 hours, 4 hours to 16 hours, 8 hours to 12 hours, 8 hours to 16 hours, 11 hours to 16 hours. Approximately, 18 gm of 20 Potassium Permanganate (KMnO4) is added slowly into the mixture with an interval of 10 minutes and again stirred for 1 hour. Again, the mixture is heated up to 50 degrees Celsius for 12 hours while stirring. Further, approximately, 400 ml of ice-cold water with 3 ml of 30% Hydrogen peroxide (H2O2) is added to stop the reaction. The mixture is washed with 25 200 ml of 5 percent Hydrochloric acid (HCI) solution and allowed to settle down for approximately 2 days. In order to remove all the impurities, the mixture is centrifuged at 5000 rpm for 4 hours and the supernatant is decanted away. The remaining solid material is washed in succession with 200 ml distilled water and 200 ml ethanol several times and repeatedly 30 centrifuged at 5000 rotations per minute (rpm) for 45 to 120 minutes. For each centrifuge, the supernatant was decanted away. After washing, the mixture was preserved in the paste form. Optionally, the natural graphite is purified by at least one of: comminution, froth flotation, reverse flotation, electrostatic separation, air classification, leaching. Optionally, the natural graphite is purified to achieve a high carbon 5 content and remove impurities. Advantageously, utilization of the graphite oxide paste result in a homogeneous graphene oxide solution which results in uniform and / or ordered graphene oxide films. Next, the graphene oxide solution is sonicated for the second time duration. Optionally, the second time duration lies in a range of 10 hours-io 20 hours. The second time duration lies in a range of 10 hours to 13 hours, 10 hours to 17 hours, 10 hours to 19 hours, 10 hours to 20 hours, 12 hours to 17 hours, 12 hours to 19 hours, 12 hours to 20 hours, 15 hours to 17 hours, 15 hours to 19 hours, 15 hours to 20 hours. Optionally, 1*0 the step of sonication is performed to exfoliate the graphene oxide CXJ is solution. Optionally, the step of sonication is performed using a sonicator £\J at the room temperature. Optionally, after sonication, the exfoliated graphene oxide solution is centrifuged at a required speed to store the graphene oxide for subsequent use. Optionally, the required speed lies in a range of 4000 rpm to 8000 rpm. The required speed lies in a range of 20 4000 rpm to 5500 rpm, 4000 to 7000 rpm, 4000 to 8000 rpm, 4500 to 5500 rpm, 4500 to 7000 rpm, 4500 to 8000 rpm, 5500 rpm, 7500 rpm, 5500 rpm to 8000 rpm, 7000 rpm to 8000 rpm. As an example, the exfoliated graphene oxide solution may be centrifuged at a speed of 8000 rpm. 25 Post sonication, the exfoliated graphene oxide solution is filtered to obtain the graphene oxide film. Optionally, the step of filtering the exfoliated graphene oxide solution is performed using at least one second filter membrane, the third surface being a surface of the at least one second filter membrane, wherein the second volume of the exfoliated graphene 30 oxide solution is passed through the at least one second filter membrane resulting in deposition of the graphene oxide film on the surface of the at least one second filter membrane. In this regard, optionally, the second volume lies in a range of 5 ml to 20 ml. the second volume lies in a range of 5 ml to 8 ml, 5 ml to 11 ml, 5 ml to 13 ml, 5 ml to 15 ml, 7 ml to 11 ml, 7 ml to 13 ml, 7 ml to 15 ml, 10 ml to 13 ml, 10 ml to 15 ml. 5 optionally, the second volume impacts the second thickness of the graphene oxide layer. For example, large second volume of the exfoliated graphene oxide solution more is the second thickness of the graphene oxide layer. Optionally, the process of filtration is performed using vacuum filtration. Optionally, the exfoliated graphene oxide solution is io passed through the at least one second filter membrane by evacuating air below the second filter membrane. The process of vacuum filtration provides a force on the exfoliated graphene oxide solution in addition to gravity and / or increases the rate of filtration. 1*0 Optionally, a given filter membrane is implemented as one of: a C\J 15 polyamide membrane, a poly(vinylidene fluoride) High Pressure Low £\J Volume (HPLV) membrane. In this regard, the given filter membrane is the first filter membrane and / or the second filter membrane. Optionally, the given filter membrane has a pore size lying in a range of 0.2 pm to 0.45 pm. In an example, the pore size of the given filter membrane may 20 be 0.2 pm. Optionally, the method further comprises transferring the graphene oxide film obtained on the third surface to a fourth surface of a substrate for obtaining a graphene oxide encapsulated substrate. Optionally, the substrate is at least one of: cellulose acetate, low density polyethylene 25 (LDPE), Polyethylene Terephthalate (PET), Polydimethylsiloxane (PDMS). Optionally, the substrate may comprise Polyethylene (PE), polyvinyl alcohol (PVA), Poly(methyl methacrylate) (PMMA), Polypropylene (PP), Polyhydroxyalkanoate (PHA), Polybutylene succinate (PBS), Polylactic acid (PLA), Polybutylene terephthalate (PBT). Optionally, the graphene 30 oxide film is transferred to the fourth surface of the substrate by a least one of: at least one of: spraying, dip-coating, rod-coating. Notably, the graphene oxide film encapsulates the fourth surface of the substrate. Advantageously, the graphene oxide film is transferred to the fourth surface for subsequent analysis and / or characterization. Optionally, the method further comprises reducing the graphene oxide 5 film deposited on the graphene oxide encapsulated substrate by one of: immersing the graphene oxide encapsulated substrate in an acidic aqueous solution having a specific concentration at a first temperature for a third time duration; exposing the graphene oxide encapsulated substrate to acidic vapor 10 at a second temperature for a fourth time duration. In this regard, the acidic aqueous solution could be at least one of: ascorbic acid, citric acid, caffeic acid. As an example, the acidic aqueous solution may be ascorbic acid aqueous solution. Optionally, the specific concentration of the acidic aqueous solution is 20 millimolar (mM) to 200 15 mM. The specific concentration of the acidic aqueous solution lies in a range of 20 mM to 80 mM, 20 mM to 130 mM, 20 mM to 170 mM, 20 mM to 200 mM, 50 mM to 130 mM, 50 mM to 170 mM, 50 mM to 200 mM, 90 mM to 130 mM, 90 mM to 170 mM, 90 mM to 200 mM, 140 mM to 170 mM, 140 mM to 200 mM. As an example, the specific concentration 20 of the acidic aqueous solution may be 20mM. Optionally, the graphene oxide encapsulated substrate is immersed in the acidic aqueous solution using at least one of a machine with a robotic arm, a robot, hands of a person. Optionally, the first temperature lies in a range of 45 degrees Celsius to 95 degrees Celsius. The first temperature lies in a range of 45 25 degrees Celsius to 60 degrees Celsius, 45 degrees Celsius to 80 degrees Celsius, 45 degrees Celsius to 95 degrees Celsius, 50 degrees Celsius to 80 degrees Celsius, 50 degrees Celsius to 95 degrees Celsius, 70 degrees Celsius to 95 degrees Celsius. As an example, the first temperature of the ascorbic acid aqueous solution may be 90 degrees Celsius. Optionally, 30 the third time duration lies in a range of 45 minutes to 4 hours. The third time duration lies in a range of 45 minutes to 60 minutes, 45 minutes to 160 minutes, 45 minutes to 200 minutes, 45 minutes to 4 hours, 60 minutes to 160 minutes, 60 minutes to 200 minutes, 1 hour to 4 hours, 100 minutes to 200 minutes, 100 minutes to 4 hours, 150 minutes to 200 minutes, 150 minutes to 240 minutes. As an example, the third time 5 duration may be four hours. Immersion of the graphene oxide film may result in loss of the oxygen containing functional groups from the graphene oxide film. Optionally, reduction of the graphene oxide film is indicated by a change in colour of the graphene oxide film from light brown to black. io Optionally, the acidic vapour is hydroiodic acid vapour. Optionally, the second temperature lies in a range of 70 degrees Celsius to 110 degrees Celsius. The second temperature lies in a range of 70 degrees Celsius to 80 degrees Celsius, 70 degrees Celsius to 100 degrees Celsius, 70 । q degrees Celsius to 110 degrees Celsius, 75 degrees Celsius to 100 c\j 15 degrees Celsius, 75 degrees Celsius to 110 degrees Celsius, 90 degrees £\J Celsius to 110 degrees Celsius. As an example, the second temperature may be 90 degrees Celsius. Optionally, the fourth time duration lies in a range of 5 minutes to 60 minutes. The fourth time duration lies in a range of 5 minutes to 15 minutes, 5 minutes to 35 minutes, 5 minutes to 50 20 minutes, 5 minutes to 60 minutes, 10 minutes to 35 minutes, 10 minutes to 50 minutes, 10 minutes to 60 minutes, 20 minutes to 50 minutes, 20 minutes to 60 minutes, 40 minutes to 60 minutes. As an example, the fourth time duration may be 30 minutes. Advantageously, the technical effect of reducing the graphene oxide film results in enhanced barrier 25 properties of the graphene oxide film against the fluids. Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", mean "including but not limited to", and do not exclude other components, integers or steps. Moreover, the so singular encompasses the plural unless the context otherwise requires; in particular, where the indefinite article is used, the specification is to be 14 02 25 understood as contemplating plurality as well as singularity, unless the context requires otherwise. Preferred features of each aspect of the invention may be as described in connection with any of the other aspects. Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the following diagrams wherein: FIG. 1 is a schematic illustration of a graphene oxide film incorporated as one or more layers within a multi-layer packaging, in accordance with an embodiment of the present invention;and FIG. 2 is a flow chart of steps of a method for manufacturing a graphene oxide film, in accordance with an embodiment of the present invention. DETAILED DESCRIPTION Referring to FIG. 1, illustrated is a schematic illustration of a graphene oxide film 106 incorporated as one or more layers within a multi-layer packaging (depicted for example as a tetra pack 108), in accordance with an embodiment of the present invention. The multi-layer packaging 108 has a plurality of layers (depicted for examples as layers 110a, 110b, 110c). FIG. 1 is merely example which should not unduly limit the scope of the claims herein. A person skilled in the art will recognize many variations, alternatives, and modifications of embodiments of the present disclosure. Referring to FIG. 2, is a flow chart of steps of a method for manufacturing 5 a graphene oxide film, in accordance with an embodiment of the present invention. At step 302, graphite oxide paste is diluted in deionized (DI) water for obtaining a graphene oxide solution. At step 304, the graphene oxide solution is sonicated for a second time duration for preparing an exfoliated graphene oxide solution. At step 306, the exfoliated graphene io oxide solution is filtered for obtaining the graphene oxide film of a second thickness on a third surface. CM CM The aforementioned steps are only Illustrative, and other alternatives can also be provided where one or more steps are added, one or more steps are removed, or one or more steps are provided in a different sequence 15 without departing from the scope of the claims herein.

Claims

1. A method of manufacturing a multi-layer packaging, the method comprising:- diluting graphite oxide paste in deionized (DI) water for obtaining a graphene oxide solution;- sonicating the graphene oxide solution for a time duration for preparing an exfoliated graphene oxide solution;- filtering the exfoliated graphene oxide solution for obtaining a film comprising graphene oxide, wherein the film has a thickness in a range of 0.5 pm to 20 pm;- manufacturing each of a plurality of layers of packaging materials that constitute the multi-layer packaging, wherein one or more layers amongst the plurality of layers comprise the film, and wherein the film is impermeable to moisture or fluids; and- assembling the plurality of layers in a required manner to form the multilayer packaging.

2. A method according to claim 1, wherein the step of filtering the exfoliated graphene oxide solution is performed using at least one filter membrane having a surface for obtaining the film, wherein a volume of the exfoliated graphene oxide solution is passed through the at least one filter membrane resulting in deposition of the film on the surface of the at least one filter membrane.

3. A method according to claim 1 or 2, further comprising synthesizing the graphite oxide paste from natural graphite.

4. A method according to claim 1 or 2 or 3, further comprising transferring the film obtained on the surface to another surface of a substrate for obtaining a graphene oxide encapsulated substrate.

5. A method according to claim 4, further comprising reducing the film deposited on the graphene oxide encapsulated substrate by one of:- immersing the graphene oxide encapsulated substrate in an acidic aqueous solution having a specific concentration at a first temperature for another time duration;- exposing the graphene oxide encapsulated substrate to acidic vapour at a second temperature for further time duration.

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