WO2016106312A2 - Graphite exfoliation in resin - Google Patents

Abstract

Provided herein is technology relating to polymer composite materials and particularly, but not exclusively, to graphene-polymer composite materials and methods for producing graphene-polymer composite materials by exfoliating graphite directly in a resin such as a liquid thermoset resin.

Description

GRAPHITE EXFOLIATION IN RESIN

The present Application claims priority to United States Provisional Patent Application Serial Number 62/095,452 filed December 22, 2014, the disclosure of which is herein incorporated by reference in its entirety.

FIELD

Provided herein is technology relating to polymer composite materials and particularly, but not exclusively, to grap he ne -polymer composite materials and methods for producing gr ap he ne -polymer composite materials by exfoliating graphite directly in a resin such as a liquid thermoset resin.

BACKGROUND

Polymer nanocomposites comprising a nanomaterial dispersed in a polymer matrix have attracted interest because they have many desirable performance attributes related to mechanical properties, electrical conductivity, thermal conductivity, gas/vapor barrier properties, etc. In particular, graphene nanoplatelets enhance a variety of important functional properties of commercially important polymers. Accordingly, polymer- graphene nanocomposites comprising a graphene dispersed in a polymer matrix have been the subject of much research and development activity in recent years.

Some current solutions for producing graphene -polymer composites include intermediate steps of producing graphene by liquid phase exfoliation of graphite in organic solvents, exfoliation of graphite in aqueous surfactant solutions, and mechanical exfoliation of graphite. Studies indicate that liquid phase exfoliation of graphite can produce single-layer and few-layer graphene nanoplatelets. In particular, a solution having a significant concentration of soluble graphene can be produced by selecting a solvent having a surface free energy to match the surface free energy of graphite.

Alternatively, surfactants can be used in water to reduce the interfacial free energy between graphene platelets to the point where significant concentrations of soluble graphene can be dissolved from graphite.

These graphene dispersion intermediates can be used to produce a polymer nanocomposite. For instance, solutions and dispersions of graphene nanoplatelets prepared from graphite by liquid phase exfoliation have been effectively used to prepare thermoset polymer composites by mixing the graphene solutions or dispersions with liquid thermoset resins, followed by removal of the solvents and curing the resins.

However, producing graphene -containing thermoset polymer composites in this way suffers from serious limitations. For example, several time-consuming and costly process steps are involved both in carrying out the liquid phase exfoliation of graphite to produce graphene and in removing unexfoliated graphite. Furthermore, the maximum concentrations of graphene provided by liquid phase exfoliation are well below 1%, thus requiring handling large volumes of liquids and extensive solvent evaporation relative to the amount of graphene and graphene-containing polymer resin produced. Finally, trace amounts (e.g., less than 0.1%) of residual solvent resulting from incomplete solvent removal can degrade the resin and compromise desirable properties of the composites. SUM MARY

Provided herein is technology relating to polymer composite materials and particularly, but not exclusively, to graphene -polymer composite materials and methods for producing graphene -polymer composite materials by exfoliating graphite directly in a resin such as a liquid thermoset resin. In particular, experiments conducted during the development of embodiments of the technology described herein indicated that graphite exfoliated directly into liquid thermoset resins by high shear mixing provided a composite material with improved characteristics. Furthermore, it was surprisingly discovered that it was unnecessary to remove the unexfoliated graphite from the resin, thereby eliminating an inefficient and costly separation step.

Data collected from experiments conducted during the development of

embodiments of the technology indicated that high shear mixing graphite into certain thermoset resins provides for a composite resin material having an improved storage modulus. In particular, the improved composite resin materials have a storage modulus that is much improved relative to the storage modulus of resins comprising graphite in the absence of high shear mixing. Also, the improved composite resin materials produced by the methods described herein do not have deleterious brittleness

characteristics that occur when significant amounts of graphite are present in current resin composites produced by extant methods. Not to be bound by theory, but it is believed that high shear mixing the graphite/resin mixture not only converts a highly performance-effective fraction of the graphite to graphene, but also reduces the particle size of the unexfoliated graphite below a critical threshold that minimizes and/or eliminates brittleness.

Accordingly, embodiments of the technology relate to methods for the preparation of a composite resin material by exfoliating graphite in a polymer (e.g., liquid thermoset resin) by high shear mixing. In some embodiments, bulk graphite is exfoliated by high shear mixing in a neat liquid thermoset resin without the use of an exfoliating solvent to produce an exfoliated graphene intermediate. Accordingly, the composite resin materials are exfoliation solvent-free. Further, the incompletely exfoliated and unexfoliated graphite are not removed from the composite resin materials. In some embodiments, the composite resin materials comprise graphite particles having a size that minimizes and/or eliminates undesirable mechanical characteristics such as brittleness.

Further, experiments were conducted during the development of embodiments of the technology to test composite resin materials that were prepared by direct exfoliation of graphite into a liquid thermoset resin and co-exfoliating multi-wall carbon nanotubes (MWCNT) into the resin with the graphite. Data collected indicated that the composite resin materials have enhanced mechanical properties and useful conductivity.

The technology is useful for producing polymer- graphene composite materials at a lower cost and reduced process complexity.

Thus, in some embodiments the technology provides a method of producing a graphene suspension in a resin, the method comprising high shear mixing a mixture of resin and graphite to produce a graphene suspension in a resin. In some embodiments, the mixture of resin and graphite comprises at least 1% graphite (w/w), e.g., at least 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40% or more graphite (w/w). In some embodiments, the graphene suspension in the resin comprises at least 0.1% graphene (w/w), e.g., at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more graphene (w/w). In some embodiments, the graphene particles have fewer than 20 atomic layers, preferably fewer than 10 atomic layers.

In some embodiments, the resin is a liquid thermoset resin. In some

embodiments, the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 1,000 to 50,000 centipoise (cP) (e.g.,

approximately 1,000; 5,000; 10,000; 15,000; 20,000; 25,000; 30,000; 35,000; 40,000;

45,000; or 50,000 cP). For example, in some embodiments the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 5,000 to 30,000 cP (e.g., approximately 5,000; 7,500; 10,000; 12,500; 15,000; 17,500; 20,000; 22,500; 25,000; 27,500; or 30,000 cP). And, in particular embodiments, the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 10,000 to 20,000 cP (e.g., approximately 10,000; 10,500;

11,000; ii,500; 12,000; 12,500; 13,000; 13,500; 14,000; 14,500; 15,000; 15,500; 16,000; 16,500; 17,000; 17,500; 18,000; 18,500; 19,000; 19,500; or 20,000 cP).

Furthermore, in some embodiments the graphene suspension in the resin comprises unexfoliated graphite particles having a size that minimizes and/or

eliminates undesirable mechanical characteristics.

In particular embodiments, graphene is not produced by exfoliation of graphite in an exfoliation solvent, e.g., in an intermediate step for producing graphene by solvent exfoliation of graphite (e.g., mixing graphite in an exfoliation solvent). Accordingly, in some embodiments the graphene suspension in the resin is exfoliation solvent-free.

In some embodiments, the mixture of resin and graphite is high shear mixed for at least 30 minutes, e.g., for at least 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, or 6 or more hours. In some embodiments, the mixture of resin and graphite is high shear mixed, e.g., mixed using a stator-rotor mixer wherein the shear gap is between 50 μπι and 150 μπι and the tip speed of the rotor is at least 400 feet/second.

Additional embodiments provide a method of producing a polymer- graphene composite material, the method comprising high shear mixing a mixture of resin and graphite to produce a graphene suspension in a resin! and curing the graphene suspension in the resin to produce a polymer-graphene composite material. In some embodiments, the mixture of resin and graphite comprises at least 1% graphite (w/w), e.g., at least 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40% or more graphite (w/w). In some

embodiments, the graphene suspension in the resin comprises at least 0.1% graphene (w/w), e.g., at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more graphene (w/w). In some embodiments, the graphene particles have fewer than 20 atomic layers, preferably fewer than 10 atomic layers. In some embodiments, the resin is a liquid thermoset resin. In some embodiments, the curing is effected by use of a chemical curing agent (e.g., a hardener), by use of incubating at increased temperature, and/or by exposure to electromagnetic radiation. In some embodiments, the graphene suspension in the resin comprises unexfoliated graphite particles having a size that minimizes and/or eliminates undesirable mechanical characteristics of the polymer- graphene composite material. In some embodiments, the graphene suspension in the resin is exfoliation solvent-free. In some embodiments, the mixture of resin and graphite is high shear mixed for at least 30 minutes, e.g., for at least 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, or 6 or more hours. In some embodiments, the mixture of resin and graphite is high shear mixed, e.g., mixed using a stator-rotor mixer wherein the shear gap is between 50 μηι and 150 μηι and the tip speed of the rotor is at least 400 feet/second. In some embodiments, the polymer- grap he ne composite material comprises at least 0.1% graphene (w/w), e.g., at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%,

I.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more graphene (w/w). In some embodiments, the graphene particles have fewer than 20 atomic layers, preferably fewer than 10 atomic layers.

In some embodiments, the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 1,000 to 50,000 centipoise (cP) (e.g., approximately 1,000; 5,000; 10,000; 15,000; 20,000; 25,000; 30,000; 35,000; 40,000; 45,000; or 50,000 cP). For example, in some embodiments the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 5,000 to 30,000 cP (e.g., approximately 5,000; 7,500; 10,000; 12,500; 15,000; 17,500; 20,000; 22,500; 25,000; 27,500; or 30,000 cP). And, in particular embodiments, the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 10,000 to 20,000 cP (e.g., approximately 10,000; 10,500;

I I, 000; ii,500; 12,000; 12,500; 13,000; 13,500; 14,000; 14,500; 15,000; 15,500; 16,000; 16,500; 17,000; 17,500; 18,000; 18,500; 19,000; 19,500; or 20,000 cP).

In some embodiments, the polymer- graphene composite material comprises unexfoliated graphite particles having a size that minimizes and/or eliminates undesirable mechanical characteristics of the polymer- graphene composite material. In some embodiments, the polymer -graphene composite material is exfoliation solvent-free.

Still further embodiments provide a method of producing a polymer-graphene composite material, the method comprising high shear mixing a mixture of resin, graphite, and multiwall carbon nanotubes to produce a suspension of graphene and exfoliated multiwall carbon nanotubes in a resin! and curing the suspension of graphene and exfoliated multiwall carbon nanotubes in a resin to produce a polymer-graphene composite material. In some embodiments, the mixture of resin, graphite, and multiwall carbon nanotubes comprises at least 1% graphite (w/w) and at least 0.1% multiwall carbon nanotubes (w/w), e.g., at least 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40% or more graphite (w/w) and at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more multiwall carbon nanotubes (w/w).

In yet further embodiments, the technology provides a method of producing a polymer -grap he ne composite material, the method comprising high shear mixing a mixture of resin and graphite to produce a suspension of graphene in a resin! adding multiwall carbon nanotubes to the suspension of graphene in a resin to produce a suspension of graphene and multiwall carbon nanotubes in a resin! high shear mixing the suspension of graphene and multiwall carbon nanotubes in a resin to produce a suspension of graphene and exfoliated multiwall carbon nanotubes! and curing the suspension of graphene and exfoliated multiwall carbon nanotubes in a resin to produce a polymer- graphene composite material. In some embodiments, the mixture of resin and graphite comprises at least 1% graphite (w/w) and the suspension of graphene and exfoliated multiwall carbon nanotubes comprises at least 0.1% multiwall carbon nanotubes (w/w), e.g., the mixture of resin and graphite comprises at least 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40% or more graphite (w/w) and the suspension of graphene and exfoliated multiwall carbon nanotubes comprises at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more multiwall carbon nanotubes (w/w).

Some embodiments provide compositions produced according to embodiments of the methods described herein. For example, in some embodiments the technology provides a polymer- graphene composite material produced by a method comprising high shear mixing a mixture of resin and graphite to produce a graphene suspension in a resin. In some embodiments, the polymer -graphene composite material is an exfoliation solvent-free polymer- graphene composite material.

Some embodiments provide a composition comprising a resin and graphene produced by a method comprising high shear mixing a mixture of resin and graphite to produce a graphene suspension in a resin. In some embodiments, the composition comprising a resin and graphene is an exfoliation-free composition comprising a resin and gra hene. That is, in some embodiments the composition comprising a resin and graphene is completely free of any added exfoliation solvents.

Some embodiments provide compositions. For example, some embodiments provide an exfoliation solvent-free composition comprising a resin and at least 1% graphene (w/w). Some embodiments provide an exfoliation solvent-free composition comprising a resin, at least 1% graphene (w/w), and at least 0.1% exfoliated multiwall carbon nanotubes (w/w). In some embodiments, the composition is an exfoliation solvent-free polymer- graphene composite material.

Finally, the technology provides embodiments of systems for producing a polymer- graphene composite material. In some embodiments, the system comprises a resin, graphite, a high shear mixer, and a curing agent. In some embodiments, the resin is a liquid thermoset resin. In some embodiments, the curing agent is a chemical curing agent. In some embodiments, the system further comprises multiwall carbon nanotubes.

Additional embodiments will be apparent to persons skilled in the relevant art based on the teachings contained herein.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present technology will become better understood with regard to the following drawings:

Fig. 1 is a bar plot showing the storage modulus of unsaturated polyester polymer composite materials prepared according to the technology described by high shear mixing resin and 10% (w/w) graphite for 0 to 3 hours.

Fig. 2 is a bar plot showing the storage modulus of unsaturated polyester polymer composite materials prepared according to the technology described by high shear mixing resin and 20% (w/w) graphite for 0 to 4 hours.

Fig. 3 is a bar plot showing the storage modulus of unsaturated polyester polymer composite materials prepared according to the technology described by high shear mixing resin and 25% (w/w) graphite for 0 to 6 hours in a large batch format.

Fig. 4 is a bar plot showing the storage modulus of epoxy polymer composite materials prepared according to the technology described by high shear mixing resin and 30% (w/w) graphite for from 0 to 4 hours.

It is to be understood that the figures are not necessarily drawn to scale, nor are the objects in the figures necessarily drawn to scale in relationship to one another. The figures are depictions that are intended to bring clarity and understanding to various embodiments of apparatuses, systems, and methods disclosed herein. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Moreover, it should be appreciated that the drawings are not intended to limit the scope of the present teachings in any way.

DETAILED DESCRIPTION

Provided herein is technology relating to polymer composite materials and particularly, but not exclusively, to graphene-polymer composite materials and methods for producing graphene-polymer composite materials by exfoliating graphite directly in a resin such as a liquid thermoset resin.

In this detailed description of the various embodiments, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the embodiments disclosed. One skilled in the art will appreciate, however, that these various embodiments may be practiced with or without these specific details. In other instances, structures and devices are shown in block diagram form. Furthermore, one skilled in the art can readily appreciate that the specific sequences in which methods are presented and performed are illustrative and it is contemplated that the sequences can be varied and still remain within the spirit and scope of the various embodiments disclosed herein. The section headings used herein are for organizational purposes only and are not to be construed as limiting the described subject matter in any way.

All literature and similar materials cited in this application, including but not limited to, patents, patent applications, articles, books, treatises, and internet web pages are expressly incorporated by reference in their entirety for any purpose. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which the various embodiments described herein belongs. When definitions of terms in incorporated references appear to differ from the definitions provided in the present teachings, the definition provided in the present teachings shall control.

Definitions

To facilitate an understanding of the present technology, a number of terms and phrases are defined below. Additional definitions are set forth throughout the detailed description.

Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrase "in one embodiment" as used herein does not necessarily refer to the same embodiment, though it may. Furthermore, the phrase "in another embodiment" as used herein does not necessarily refer to a different embodiment, although it may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.

In addition, as used herein, the term "or" is an inclusive "or" operator and is equivalent to the term "and/or" unless the context clearly dictates otherwise. The term "based on" is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of "a", "an", and "the" include plural references. The meaning of "in" includes "in" and "on."

As used herein, "graphene" refers to an allotrope of carbon having a structure that is a single planar sheet (an "atomic layer") of sp2-bonded carbon atoms arranged in a honeycomb crystal lattice. As used herein, the term graphene includes but is not limited to graphene in the form of a one -atom -thick (monolayer) sheet, e.g., a graphene sheet that is one atomic layer thick. As such, the term "graphene" also refers to the form of graphene in which many graphene sheets are stacked together, e.g., as present in the crystalline or "flake" form of graphite. Accordingly, as used herein, the term "graphene" refers to monolayer (single layer) and/or multilayer graphene with a nanoscale thickness (e.g., graphene having fewer than 20 atomic layers and preferably fewer than 10 atomic layers).

As used herein, the term "pristine" means not functionalized, modified, or chemically reacted with other elements such as oxygen.

As used herein, a "nanomaterial" is a material having one or more external dimensions in the size range of 1 nm to 100 nm. The "morphology" of a nanomaterial refers to the shape of the discrete nanomaterial particles.

As used herein, a nanomaterial is described as "intercalated" when the sheets of the nanomaterial are substantially organized in parallel and a nanomaterial is described as "exfoliated" when this arrangement has been lost.

As used herein, the term "resin" refers to liquid materials that are capable of hardening permanently, e.g., by polymerization. For instance, some "resins" are thermosetting plastics and the term "resin" may refer to the reactant or product, or both. The term "resin" may refer to one of two monomers in a copolymer (the other being called a "hardener", e.g., as in an epoxy resin). For those thermosetting plastics that require only one monomer, the monomer compound is the "resin". A "resin composition", as used herein, refers to a raw material composition comprising a resin and, optionally, one or more other chemicals, materials, solvents, etc.

As used herein, a "polymerizer" is a chemical reagent that effects the

polymerization of a monomer, mixture of monomers, an oligomer, mixture of oligomers, or mixtures thereof into a polymer. Polymerizers as described herein are also widely referred to as "curing agents" or "hardeners". Exemplary polymerizers may comprise, but are not limited to, organic peroxides (e.g., benzoyl peroxide), amines (e.g., ethylene diamine), sulfides, anhydrides, and many other compounds that can effect

polymerization.

As used herein, the term "high shear mixing" refers to mixing that produces a shear rate of greater than 1.0 x 10⁵ sec^-1.

Description

In some embodiments of the technology described herein, the technology is related to polymer-graphene composite materials and methods for the production of polymer- graphene composite materials. In particular embodiments, methods are provided for producing a polymer-graphene composite material by exfoliating graphite in a polymer (e.g., resin) by high shear mixing. In some embodiments, the technology produces an exfoliation solvent-free polymer-graphene composite material. In some embodiments, the technology produces a polymer-graphene composite material from a mixture comprising graphite at greater than 1% (w/w), e.g., greater than 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or more, in a resin. Although the disclosure herein refers to certain illustrated embodiments, it is to be understood that these embodiments are presented by way of example and not by way of limitation.

"Exfoliation solvent-free" compositions

The technology is related to resins comprising graphene (e.g., suspensions of graphene in a resin) and polymer-graphene composite materials (e.g., polymer-graphene composite materials cured from suspensions of graphene in a resin). The technology is further related to methods of producing suspensions of graphene in a resin and producing polymer-graphene composite materials.

Some current methods for producing polymer-graphene composites typically involve a step of producing solvent exfoliated graphene by mixing graphite in an exfoliation solvent to produce a slurry intermediate comprising graphene in exfoliation solvent. Then, the graphene is concentrated by removing some portion of the solvent, e.g., by evaporation, filtration, etc., to produce a graphene intermediate. Then, the graphene intermediate (e.g., comprising the graphene in some remainder of the exfoliation solvent) is used to prepare a resin comprising graphene and, subsequently, to produce a polymer -graphene composite material. In some alternative methods, an exfoliation solvent is added with graphite to a resin and mixed to produce a suspension of graphene in a resin. Using such a method produces a suspension of graphene in a resin that also comprises added exfoliation solvent. In both methods, removing the solvent from the slurry, from the suspension of graphene in the resin, and/or from the polymer- graphene composite material is difficult, costly, and time consuming! further, the small amounts of added exfoliation solvent that remain in the polymer-graphene composite materials can compromise the desirable characteristics (e.g., physical, chemical, optical, electrical, etc. characteristics) of the polymer-graphene composite materials.

In contrast, the technology provided herein provides an unexpected and important improvement over extant methods and compositions. In particular, the technology provides compositions that do not comprise added exfoliation solvents and provides related methods for producing such compositions that do not involve producing any of the aforementioned intermediate compositions of exfoliated graphene in an exfoliation solvent and without adding an exfoliation solvent or any other solvents to the resin or suspension of graphene in the resin. Accordingly, embodiments of compositions comprising a suspension of graphene in a resin and embodiments of compositions comprising a polymer-graphene composite as described herein do not comprise any solvents other than, or any solvent in addition to, solvents that were present in the resin composition used to make the suspensions of graphene in the resin and that were subsequently carried forward into the suspensions of graphene in the resin and/or the polymer-graphene composites.

Thus, as used herein, the term "exfoliation solvent" refers to a solvent that is used to exfoliate graphite (e.g., by solvent exfoliation methods) to produce graphene in an intermediate step prior to mixing the graphite or graphene with a polymer or a resin. Thus, a composition that is "exfoliation solvent-free" may comprise a solvent that was originally present in the resin composition used to prepare the suspension of graphene in the resin, but a composition that is "exfoliation solvent-free" does not comprise any additional type (e.g., any additional chemical species) or any additional amount of solvent, e.g., from an independent, intermediate solvent exfoliation step wherein graphite and exfoliation solvent are mixed to produce solvent-exfoliated graphene. Examples of exfoliation solvents include, but are not limited to, a pyrrolidone, e.g., an N-alkyl-pyrrolidone, e.g., N-methyl pyrrolidone! or an N-alkenyl pyrrolidone, e.g., N-vinyl pyrrolidone. Other examples of exfoliation solvents used to produce graphene from graphite are described in U.S. Pat. Appl. Pub. No. 2011/0117361. As used herein, a polymer or a resin is not an "exfoliation solvent".

Accordingly, as used herein, the term "exfoliation solvent-free" means that a material (e.g., such as a suspension of graphene in a resin or a polymer- graphene composite material as described herein) does not comprise any added exfoliation solvent (e.g., such as exfoliation solvents used in extant methods to produce exfoliated graphene). For example, in some embodiments, the term "exfoliation solvent-free" means that a material (e.g., such as a suspension of graphene in a resin or a polymer- graphene composite material as described herein) may comprise a solvent that is or was present in the resin composition that was mixed with graphite to prepare a suspension of graphene in the resin in an amount less than the amount in the resin composition, but does not comprise additional solvent or other solvents.

In some embodiments, solvents present in the resin composition are

polymerizable solvents and these polymerizable solvents are subsequently polymerized in the polymer- graphene composite materials upon curing. Accordingly, in some embodiments the polymer-graphene composite materials are free of unpolymerized solvents (e.g., free of monomer solvents) or comprise unpolymerized solvents (e.g., monomer solvents) in a low (e.g., trace) amount that does not compromise the improved characteristics of the suspensions of graphene in the resin and, in particular, does not compromise the improved characteristics of the polymer-graphene composites provided herein. Further, in some embodiments, solvents present in the resin composition are non-polymerizable solvents. Accordingly, in some embodiments the polymer-graphene composite materials are free of non-polymerizable solvents or comprise non- polymerizable solvents in a low (e.g., trace) amount that does not compromise the improved characteristics of the suspensions of graphene in the resin and, in particular, does not compromise the improved characteristics of the polymer-graphene composites provided herein.

Some particular embodiments provide an exfoliation solvent-free polymer- graphene composite material that does not comprise a non-polymerizable solvent or that does not comprise an unpolymerized solvent (e.g., a monomer solvent). Some particular embodiments provide an exfoliation solvent-free polymer-graphene composite material that comprises a non-polymerizable solvent or that comprises an unpolymerized solvent (e.g., monomer solvent) in a low (e.g., trace) amount that does not compromise the improved characteristics of the polymer- graphene composites provided herein.

Some particular embodiments provide an exfoliation solvent-free polymer- graphene composite material comprising an amount of a non-polymerizable solvent or comprising an amount of an unpolymerized solvent (e.g., monomer solvent) that is less than 0.1% of the composition, e.g., less than 0.09%, 0.08%, 0.07%, 0.06%, 0.05%, 0.04%, 0.03%, 0.02%, 0.01%, 0.009, 0.008%, 0.007%, 0.006%, 0.005%, 0.004%, 0.003%, 0.002%, or 0.001% (w/w) of the composition. Some particular embodiments provide an exfoliation solvent-free polymer-graphene composite material comprising an amount of a non- polymerizable solvent or comprising an amount of an unpolymerized solvent (e.g., monomer solvent) that does not effectively, substantially, and/or significantly negatively affect the desirable characteristics of the polymer-graphene composite material.

Some particular embodiments provide an exfoliation solvent-free suspension of graphene in a resin that does not comprise a solvent in an amount greater that the amount of said solvent in the resin composition that was used to prepare the suspension of graphene in the resin. Some particular embodiments provide an exfoliation solvent- free suspension of graphene in a resin that does not comprise any specific chemical species of solvent that was not present in the resin composition that was used to prepare the suspension of graphene in the resin.

Some particular embodiments provide a suspension of graphene in a solution of thermoplastic resin in a volatile solvent (i.e., not a typical exfoliation solvent as defined herein) that can be easily removed by evaporation to provide a solid graphene/polymer resin composite that is essentially free of solvent or contains such a low level of solvent as to not negatively impact the polymer composite properties. Preferred thermoplastic resins/polymers are described above. Preferred volatile solvents are solvents with a boiling point of less than 100 degrees Celsius at atmospheric pressure and include, but are not limited to, diethyl ether, tetrahydrofuran (THF), methanol hexane, pentane and acetone. Methods

Some embodiments provide methods for producing a polymer-graphene composite material. For example, some embodiments are related to a method comprising mixing a resin (e.g., a liquid polymerizable resin) and graphite (e.g., graphite powder) to produce a suspension of graphite in the resin. Further, embodiments of methods comprise high shear mixing the suspension of graphite in the resin for at least 15 minutes or more to produce a suspension of graphene in a resin. Some embodiments comprise high shear mixing the suspension of graphite in the resin for at least 30 minutes, or for 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, or 6 or more hours. Some embodiments comprise high shear mixing the suspension of graphite in the resin at a shear rate of at least 1 x 10⁵ sec^-1. Some embodiments comprise high shear mixing the suspension of graphite in the resin using a stator-rotor mixer wherein the shear gap is between 50 μηι and 150 μηι and the tip speed of the rotor is at least 400 feet/second. For example, the tip speed of the rotor is at least 500 feet/second, 600 feet/second, 700 feet/second, 800 feet/second, or more. In some embodiments, the suspension of graphite in the resin is cooled prior to high shear mixing, e.g., cooled to a temperature of less than 20°C, less than 15°C, less than 10°C, less than 9°C, less than 8°C, less than 7°C, less than 6°C, less than 5°C, less than 4°C, less than 3°C, less than 2°C, or less than 1°C. In some embodiments, the suspension of graphite in the resin is continuously cooled during the mixing period to limit the maximum temperature during mixing to, e.g., 25°C, 30°C, 35°C, 40°C, 50°C, 60°C, 70°C, or 80°C.

In some embodiments, the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 1,000 to 50,000 centipoise (cP) (e.g., approximately 1,000; 5,000; 10,000; 15,000; 20,000; 25,000; 30,000; 35,000; 40,000; 45,000; or 50,000 cP). For example, in some embodiments the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 5,000 to 30,000 cP (e.g., approximately 5,000; 7,500; 10,000; 12,500; 15,000; 17,500; 20,000; 22,500; 25,000; 27,500; or 30,000 cP). And, in particular embodiments, the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 10,000 to 20,000 cP (e.g., approximately 10,000; 10,500;

11,000; ii,500; 12,000; 12,500; 13,000; 13,500; 14,000; 14,500; 15,000; 15,500; 16,000; 16,500; 17,000; 17,500; 18,000; 18,500; 19,000; 19,500; or 20,000 cP).

Embodiments of methods comprise mixing a resin (e.g., a liquid polymerizable resin) and graphite (e.g., graphite powder) to produce a suspension of graphite in the resin comprising at least 1% graphite (w/w). Some embodiments of methods comprise mixing a resin (e.g., a liquid polymerizable resin) and graphite (e.g., graphite powder) to produce a suspension of graphite in the resin comprising at least 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40% or more graphite (w/w). High shear mixing of the suspension of graphite in the resin produces a suspension of graphene in the resin comprising at least 0.1% graphene (w/w), e.g., at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more graphene (w/w). In some embodiments, the graphene particles have fewer than 20 atomic layers, preferably fewer than 10 atomic layers. In some embodiments, the suspension of graphene in the resin comprises unexfoliated graphite. In some

embodiments, the suspension of graphene in the resin comprises unexfoliated graphite particles having a size that minimizes and/or eliminates undesirable mechanical characteristics such as brittleness.

In particular embodiments, an added exfoliation solvent is not used to exfoliate graphite to produce graphene. Accordingly, in some embodiments the suspension of graphene in the resin is exfoliation solvent-free. That is, in some embodiments the suspension of graphene in the resin is completely free of added exfoliation solvents.

Some embodiments relate to polymer- graphene composite materials that further comprise other materials (e.g., other nanomate rials). For example, some embodiments are related to polymer- graphene composite materials that further comprise multiwall carbon nanotubes. For example, some embodiments are related to a method comprising mixing a resin (e.g., a liquid polymerizable resin), graphite (e.g., graphite powder), and multiwall carbon nanotubes to produce a suspension of graphite and multiwall carbon nanotubes in the resin.

Some embodiments of methods comprise high shear mixing the suspension of graphite and multiwall carbon nanotubes in the resin for at least 15 minutes or more. Some embodiments comprise high shear mixing the suspension of graphite and multiwall carbon nanotubes in the resin for at least 30 minutes, or for 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, or 6 or more hours. Some embodiments comprise high shear mixing the suspension of graphite and multiwall carbon nanotubes in the resin using a stator-rotor mixer wherein the shear gap is between 50 μηι and 150 μηι and the tip speed of the rotor is at least 400 feet/second. For example, the tip speed of the rotor is at least 500 feet/second, 600 feet/second, 700 feet/second, 800 feet/second, or more. In some embodiments, the suspension of graphite and multiwall carbon nanotubes in the resin is cooled prior to high shear mixing, e.g., cooled to a temperature of less than 20°C, less than 15°C, less than 10°C, less than 9°C, less than 8°C, less than 7°C, less than 6°C, less than 5°C, less than 4°C, less than 3°C, less than 2°C, or less than 1°C. In some embodiments, the suspension of graphite in the resin is continuously cooled during the mixing period to limit the maximum temperature during mixing to, e.g., 25°C, 30°C, 35°C, 40°C, 50°C, 60°C, 70°C, or 80°C.

In some embodiments, the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 1,000 to 50,000 centipoise (cP) (e.g., approximately 1,000; 5,000; 10,000; 15,000; 20,000; 25,000; 30,000; 35,000; 40,000; 45,000; or 50,000 cP). For example, in some embodiments the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 5,000 to 30,000 cP (e.g., approximately 5,000; 7,500; 10,000; 12,500; 15,000; 17,500; 20,000; 22,500; 25,000; 27,500; or 30,000 cP). And, in particular embodiments, the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 10,000 to 20,000 cP (e.g., approximately 10,000; 10,500;

11,000; ii,500; 12,000; 12,500; 13,000; 13,500; 14,000; 14,500; 15,000; 15,500; 16,000; 16,500; 17,000; 17,500; 18,000; 18,500; 19,000; 19,500; or 20,000 cP).

Embodiments of methods comprise mixing a resin (e.g., a liquid polymerizable resin), graphite (e.g., graphite powder), and multiwall carbon nanotubes to produce a suspension of graphite and carbon nanotubes in the resin comprising at least 1% graphite (w/w) and at least 0.1% multiwall carbon nanotubes. Some embodiments of methods comprise mixing a resin (e.g., a liquid polymerizable resin), graphite (e.g., graphite powder), and multiwall carbon nanotubes to produce a suspension of graphite and multiwall carbon nanotubes in the resin comprising at least 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40% or more graphite (w/w) and at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more multiwall carbon nanotubes (w/w).

Further, high shear mixing of the suspension of graphite and multiwall carbon nanotubes in the resin produces a suspension of graphene in the resin comprising at least 0.1% graphene (w/w), e.g., at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more graphene (w/w). In some embodiments, the graphene particles have fewer than 20 atomic layers, preferably fewer than 10 atomic layers. In some embodiments, high shear mixing of the suspension of graphite and multiwall carbon nanotubes in the resin produces a suspension of graphene and exfoliated multiwall carbon nanotubes in the resin comprising at least 0.1% graphene (w/w), e.g., at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more graphene (w/w) and at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more exfoliated multiwall carbon nanotubes (w/w). In some embodiments, the graphene particles have fewer than 20 atomic layers, preferably fewer than 10 atomic layers. In some embodiments, the suspension of graphene in the resin comprises unexfoliated graphite and/or unexfoliated multiwall carbon nanotubes. In some embodiments, the suspension of graphene in the resin comprises unexfoliated graphite particles having a size that minimizes and/or eliminates undesirable mechanical characteristics such as brittleness. In particular embodiments, an exfoliation solvent is not added to exfoliate graphite to produce graphene. Accordingly, in some embodiments the suspension of graphene and multiwall carbon nanotubes in the resin is exfoliation solvent-free. That is, in some embodiments the suspension of graphene and multiwall carbon nanotubes in the resin is completely free of added exfoliation solvents.

Some embodiments are related to a method comprising mixing a resin (e.g., a liquid polymerizable resin) and graphite (e.g., graphite powder) to produce a suspension of graphite in the resin, high shear mixing the suspension of graphite in the resin to produce a suspension of graphene in the resin, adding multiwall carbon nanotubes to the suspension of graphene in the resin to produce a suspension of graphene and multiwall carbon nanotubes in the resin, and then high shear mixing the suspension of graphene and multiwall carbon nanotubes in the resin to produce a suspension of graphene and exfoliated multiwall carbon nanotubes in the resin. For example, some embodiments of methods comprise mixing a resin (e.g., a liquid polymerizable resin) and graphite (e.g., graphite powder) to produce a suspension of graphite in the resin comprising at least 1% graphite (w/w). Some embodiments of methods comprise mixing a resin (e.g., a liquid polymerizable resin) and graphite (e.g., graphite powder) to produce a suspension of graphite in the resin comprising at least 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40% or more graphite (w/w). High shear mixing of the suspension of graphite in the resin produces a suspension of graphene in the resin comprising at 0.1% graphene (w/w), e.g., at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more graphene (w/w). In some embodiments, the graphene particles have fewer than 20 atomic layers, preferably fewer than 10 atomic layers. Then, multiwall carbon

nanotubes are added to the suspension of graphene in the resin to produce a suspension of graphene and multiwall carbon nanotubes in the resin comprising at least 0.1% graphene (w/w), e.g., at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more graphene (w/w) and at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more multiwall carbon nanotubes (w/w). In some embodiments, the graphene particles have fewer than 20 atomic layers, preferably fewer than 10 atomic layers.

In some embodiments, the suspension of graphene in the resin comprises unexfoliated graphite and/or unexfoliated multiwall carbon nanotubes. In some embodiments, the suspension of graphene in the resin comprises unexfoliated graphite particles having a size that minimizes and/or eliminates undesirable mechanical characteristics such as brittleness. In particular embodiments, an exfoliation solvent is not added to exfoliate graphite to produce graphene. Accordingly, in some embodiments the suspension of graphene and multiwall carbon nanotubes in the resin is exfoliation solvent-free. That is, in some embodiments the suspension of graphene and multiwall carbon nanotubes in the resin is completely free of added exfoliation solvents.

Some embodiments further provide polymerizing (or, alternatively, "curing") a suspension of graphene in a resin, e.g., a suspension of graphene in a resin comprising multiwall carbon nanotubes). In some embodiments, polymerizing comprises adding a polymerizer to a suspension of graphene in a resin and mixing the polymerizer and the suspension of graphene in the resin.

In some embodiments, polymerizing comprises incubating a suspension of graphene in a resin at a temperature of greater than 50°C, e.g., greater than 55°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or more for more than 1 hour, e.g., more than 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more hours. In some embodiments, polymerizing comprises incubating a suspension of graphene in a resin at a plurality of temperatures of greater than 50°C, e.g., greater than 55°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or more for more than 1 hour, e.g., more than 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more hours. For example, some embodiments comprise incubating a suspension of graphene in a resin at a first temperature greater than 50°C, e.g., greater than 55°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or more for more than 1 hour, e.g., more than 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more hours and then incubating the suspension of graphene in the resin at a second temperature greater than 50°C, e.g., greater than 55°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or more for more than 1 hour, e.g., more than 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more hours.

In some embodiments, polymerizing comprises exposing the suspension of graphene in a resin to electromagnetic radiation, e.g., ultraviolet radiation.

In some embodiments, a solid thermoplastic polymer is dissolved in a volatile solvent to produce a viscous polymer/solvent solution or resin which is mixed with graphite powder to form a suspension of graphite in the polymer/solvent solution. The suspension is then high-shear mixed for at least 15 minutes or more to produce a suspension of graphene in the polymer/solvent solution after which the volatile solvent is removed by evaporation to provide a solid thermoplastic graphene/polymer composite. Preferred thermoplastic resins/polymers are described above. Preferred volatile solvents are solvents with a boiling point of less than 100 degrees Celsius at atmospheric pressure and include, but are not limited to, diethyl ether, tetrahydrofuran (THF), methanol hexane, pentane and acetone.

In some embodiments, the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 1,000 to 50,000 centipoise (cP) (e.g., approximately 1,000; 5,000; 10,000; 15,000; 20,000; 25,000; 30,000; 35,000; 40,000; 45,000; or 50,000 cP). For example, in some embodiments the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 5,000 to 30,000 cP (e.g., approximately 5,000; 7,500; 10,000; 12,500; 15,000; 17,500; 20,000; 22,500; 25,000; 27,500; or 30,000 cP). And, in particular embodiments, the viscosity of the resin and/or a composition comprising the resin prior to adding the graphite is approximately 10,000 to 20,000 cP (e.g., approximately 10,000; 10,500; 11,000; ιι,5θθ; 12,000; 12,500; 13,000; 13,500; 14,000; 14,500; 15,000; 15,500; 16,000; 16,500; 17,000; 17,500; 18,000; 18,500; 19,000; 19,500; or 20,000 cP).

Graphite

The technology is not limited in the types and/or sources of graphite. For example, the graphite used to produce graphene may be natural or synthetic. The graphite may be in the alpha (hexagonal) and/or beta (rhombohedral) forms, and may be either flat or buckled. The alpha form is convertible to the beta form through mechanical treatment; the beta form is convertible to the alpha form by heating above 1300°C. Natural graphite (e.g., obtained by mining and purification of graphite -containing rock) may be, e.g., crystalline flake graphite, amorphous graphite, lump graphite (also called vein graphite), or mixtures of these forms. Synthetic graphite may be, e.g., high-quality (e.g., highly ordered pyrolytic graphite or highly oriented pyrolytic graphite) graphite, e.g., having an angular spread between the graphite sheets of less than 1°. Synthetic graphite may be produced by heating carborundum, e.g., to temperatures above 4000°C. In some embodiments, the graphite is produced by recycling graphite -containing manufactures (e.g., electrodes). Commercial sources of graphite include, e.g., Technical Grade Graphite from Sargent Chemical Company! a common, commercial 350 Mesh Mr. Zip Graphite Powder from AGS Corporation of Michigan! Asbury Carbons A-625 synthetic graphite, and/or synthetic graphite powder from, e.g., Sigma-Aldrich.

Resins and polymers

The technology is not limited in the resin that is used to make the polymer-graphene composite materials. In some embodiments, the resin is a thermoplastic resin, a thermoset resin, and/or an elastomer resin. In some embodiments, the resin is a liquid thermoset resin. In some embodiments, the resin is an unsaturated polyester resin. In some embodiments, the resin is an epoxy resin. In some embodiments, the resin is a vinyl ester resin. In some embodiments, the resin is a thermoset polyurethane resin. In some embodiments, the resin is an alkyl cyanoacrylate resin. In some embodiments, the resin is a propylene resin. In some embodiments, the resin is an ester resin, an amide resin, a styrene resin, a vinyl resin (e.g., a vinyl chloride resin), an imide resin, a dimethylsiloxane resin, an olefin resin, a carbonate resin, a nitrile rubber resin, a styrene -co -acrylic acid resin, a urethane resin, a silicone resin, an ethylene -co -vinyl acetate resin, a methylmethacrylate resin, a butyl rubber resin, an acrylic rubber resin, an N-vinyl pyrrolidone resin, an ethylene oxide resin, an ethylene -propylene -diene monomer resin, a styrene butadiene rubber resin, an ethylene-co-octene resin, a halobutyl rubber resin, a silylated-sulfonated ether ether ketone resin, a benzimidizole resin, a fluorinated benzimidizole resin, a sulfonated styrene ethylene butylene styrene resin, a hydroxylated monomer resin, a hyperbranched monomer resin, a sulfonated ether ether ketone resin, a sulfonated benzimidazole copolymer resin, a phosphoric acid doped benzimidazole resin, a sulfonated arybenethioether-sulfone resin, a sulfonated benzimidazole resin, a phenylene-vinylene resin, a thiopene resin, a fluorene resin, an aniline resin, a pyrrole resin, an amidoamine dendrimer resin, an acrylamide resin, a vinyl ester resin, an unsaturated ester resin, or a styrene butadiene resin. In addition, the technology finds use with monomers such as amino acids, sugars, and nucleotides (deoxynucleotides and ribodeoxynucleotides).

Accordingly, in some embodiments, the technology produces a polymer

comprising graphene in a thermoplastic, a thermoset, and/or an elastomer polymer. Furthermore, in some embodiments, the polymer comprising graphene is an

unsaturated polyester polymer. In some embodiments, the polymer comprising graphene is an epoxy polymer. In some embodiments, the polymer comprising graphene is a polypropylene. In some embodiments, the polymer comprising graphene is a polyester, a polyamide, a polystyrene, a polyvinyl (e.g., a polyvinyl chloride), a polyimide, a polydimethylsiloxane, a polyolefin, a polycarbonate, a nitrile rubber, a poly(styrene-co- acrylic acid), a polyurethane, a silicone, a poly(ethylene -co -vinyl acetate), a

poly(methylmethacrylate), a butyl rubber, an acrylic rubber, a poly(N-vinyl pyrrolidone), a poly(ethylene oxide), an ethylene -propylene -diene monomer rubber, natural rubber, styrene butadiene rubber, poly(ethylene-co-octene), halobutyl rubber, silylated- sulfonated poly(ether ether ketone), poly(benzimidizole), fluorinated poly(benzimidizole), sulfonated polystyrene ethylene butylene polystyrene, hydroxylated polymers, hyperbranched polymers, cross linked sulfonated poly(ether ether ketone), sulfonated polybenzimidazole copolymer, phosphoric acid doped polybenzimidazole, sulfonated polyarybenethioether-sulfone, sulfonated polybenzimidazole, poly(phenylene-vinylene), polythiopene, polyfluorene, polyaniline, polypyrrole, polyamidoamine dendrimer, polyacrylamide, a vinyl ester, an unsaturated polyester, or a polystyrene butadiene. In addition, the technology finds use with biomolecules such as proteins, DNA, RNA, lipids, sugars, and crystalline cellulose. Resin-graphite and resin-graphene suspensions

Some embodiments are related to a composition comprising a resin and graphite. Some embodiments are related to a composition comprising a resin and graphene, e.g., a suspension of graphene in a resin produced by a method comprising high shear mixing graphite and a resin as described herein (e.g., without an intermediate step of exfoliating graphite in an exfoliation solvent to produce graphene).

Some embodiments provide a suspension of graphite in a resin comprising at least 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40% or more graphite (w/w). Some embodiments provide a suspension of graphene in a resin comprising at least 0.1% graphene (w/w), e.g., at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more graphene (w/w). In some embodiments, the graphene particles have fewer than 20 atomic layers, preferably fewer than 10 atomic layers. In some embodiments, the suspension of graphene in the resin comprises unexfoliated graphite. In some embodiments, the suspension of graphene in the resin comprises unexfoliated graphite particles having a size that minimizes and/or eliminates undesirable mechanical characteristics such as brittleness. In some embodiments the suspension of graphene in the resin is exfoliation solvent-free. That is, in some embodiments the suspension of graphene in the resin is completely free of added exfoliation solvents.

Some embodiments relate to polymer- graphene composite materials that further comprise other materials (e.g., other nanomaterials). For example, some embodiments are related to polymer- graphene composite materials that further comprise multiwall carbon nanotubes.

For example, some embodiments provide a suspension of graphite and carbon nanotubes in a resin comprising at least 1% graphite (w/w) and at least 0.1% multiwall carbon nanotubes. Some embodiments provide a suspension of graphite and multiwall carbon nanotubes in the resin comprising at least 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40% or more graphite (w/w) and at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more multiwall carbon nanotubes (w/w). Some embodiments provide a suspension of graphene and exfoliated multiwall carbon nanotubes in a resin comprising at least 0.1% graphene (w/w), e.g., at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more graphene (w/w) and at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more exfoliated multiwall carbon nanotubes (w/w). In some embodiments, the graphene particles have fewer than 20 atomic layers, preferably fewer than 10 atomic layers. In some embodiments, the suspension of graphene in the resin comprises unexfoliated graphite and/or unexfoliated multiwall carbon nanotubes. In some embodiments, the suspension of graphene in the resin comprises unexfoliated graphite particles having a size that minimizes and/or eliminates undesirable mechanical characteristics such as brittleness. In particular embodiments, an exfoliation solvent is not added to exfoliate graphite to produce graphene. Accordingly, in some embodiments the suspension of graphene and multiwall carbon nanotubes in the resin is exfoliation solvent-free. That is, in some embodiments the suspension of graphene and multiwall carbon nanotubes in the resin is completely free of added exfoliation solvents.

Polymer-graphene composite materials

Some embodiments are related to a composition comprising a polymer and graphene, e.g., a suspension of graphene in a polymer produced by a method comprising high shear mixing graphite and a resin as described herein (e.g., without exfoliating graphite in an exfoliation solvent) to produce a suspension of graphene in the resin and, in some embodiments, curing the suspension of graphene in the resin to produce a suspension of graphene in a polymer.

Some embodiments provide a suspension of graphene in a polymer comprising at least 0.1% graphene (w/w), e.g., at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more graphene (w/w). In some embodiments, the graphene particles have fewer than 20 atomic layers, preferably fewer than 10 atomic layers. In some embodiments, the suspension of graphene in the polymer comprises unexfoliated graphite. In some embodiments, the suspension of graphene in the polymer comprises unexfoliated graphite particles having a size that minimizes and/or eliminates undesirable mechanical characteristics such as brittleness. In some embodiments the suspension of graphene in the polymer is exfoliation solvent-free. That is, in some embodiments the suspension of graphene in the polymer is completely free of added exfoliation solvents.

Some embodiments relate to polymer- graphene composite materials that further comprise other materials (e.g., other nanomaterials). For example, some embodiments are related to polymer-graphene composite materials that further comprise exfoliated multiwall carbon nanotubes.

Some embodiments provide a suspension of graphene and exfoliated multiwall carbon nanotubes in a polymer comprising at least 0.1% graphene (w/w), e.g., at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more graphene (w/w) and at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4.0% or more exfoliated multiwall carbon nanotubes (w/w). In some embodiments, the graphene particles have fewer than 20 atomic layers, preferably fewer than 10 atomic layers. In some embodiments, the suspension of graphene in the polymer comprises unexfoliated graphite and/or unexfoliated multiwall carbon nanotubes. In some embodiments, the suspension of graphene in the polymer comprises unexfoliated graphite particles having a size that minimizes and/or eliminates undesirable mechanical characteristics such as brittleness. In particular embodiments, an exfoliation solvent is not added to exfoliate graphite to produce graphene. Accordingly, in some embodiments the suspension of graphene and multiwall carbon nanotubes in the polymer is exfoliation solvent-free. That is, in some embodiments the suspension of graphene and multiwall carbon nanotubes in the polymer is completely free of added exfoliation solvents.

In some embodiments, the polymer-graphene composite materials described herein have an improved storage modulus. In some embodiments, the polymer-graphene composite materials have an improved impact strength. In some embodiments, the polymer-graphene composite materials comprising exfoliated multiwall carbon nanotubes have characteristics related to improved electrostatic dissipation. For example, in some embodiments, the polymer-graphene composite materials described herein have a storage modulus that is increased at least 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or more relative to the storage modulus of materials comprising the same polymer without comprising graphene (e.g., a graphene-free polymer). In some embodiments, the polymer-graphene composite materials described herein have a storage modulus that is increased at least 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or more relative to the storage modulus of materials comprising graphite and the same polymer, but that have not been high shear mixed.

In some embodiments, the polymer-graphene composite materials have an impact strength that is similar or within 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25% of the impact strength of materials comprising the same polymer without comprising graphene (e.g., a graphene- free polymer).

In some embodiments, the polymer-graphene composite materials comprising exfoliated multiwall carbon nanotubes have characteristics related to electrostatic dissipation, e.g., a volume resistivity of less than 10⁸ Ohm-cm. Examples

During the development of embodiments of the technology described herein,

experiments were conducted to test the production of polymer-graphene composites by exfoliation of graphite directly in a liquid thermoset resin (e.g., without the use of solvent exfoliation to provide an exfoliated graphene solution intermediate). In particular, bulk graphite was exfoliated in a neat thermoset resin with no other solvent present. Data collected during the development of embodiments of the technology indicate that the mechanical characteristics of the polymer nanocomposites was dependent on processing variables such as, e.g., graphite loading, viscosity, and mixing time. Furthermore, the conditions for producing improved polymer-graphene composites were not predictable.

Materials and Methods

Exfoliation of graphite into unsaturated polyester resin at 10% ( w/w) graphite loading Unsaturated polyester resin (PCCR 741-6510 isophthalic base pultrusion resin, 152.3 g) was added to an 8-ounce glass jar. Graphite powder (Asbury A625 synthetic graphite, 16.89 g) was mixed into the liquid resin by manual mixing until a uniformly mixed suspension was obtained. The glass jar was cooled at 5°C, and the suspension was then mixed using a Silverson L5M overhead high shear lab mixer fitted with a 1-inch tubular mixing assembly and a general purpose disintegrating mixing head. The suspension was mixed at 8000 rpm for three hours. Throughout the mixing, the jar was continuously moved in relation to the mixing head to ensure mixing of the entire sample volume and thus minimize and/or eliminate "dead zones" in the mixture. Samples of the mixture were removed before the high shear mixing was started (graphite control) and after one, two, and three hours of high shear mixing ("0 hour shear", "1 hour shear", "2 hour shear, "and 3 hour shear" samples).

Exfoliation of graphite into unsaturated polyester resin at 20% (w/w) graphite loading Unsaturated polyester resin (PCCR 741-6510 isophthalic base pultrusion resin,

141.97 g) was added to an 8-ounce glass jar. Graphite powder (Asbury A625 synthetic graphite, 35.49 g) was mixed into the liquid resin by manual mixing until a uniformly mixed suspension was obtained. The glass jar was cooled at 5°C, and the suspension was then mixed using a Silverson L5M overhead high shear lab mixer fitted with a 1-inch tubular mixing assembly and general purpose disintegrating mixing head. The suspension was mixed at 8000 rpm for four hours. Throughout the mixing, the jar was continuously moved in relation to the mixing head to ensure mixing of the entire sample volume and thus minimize and/or eliminate "dead zones" in the mixture. Samples of the mixture were removed before the high shear mixing was started (graphite control) and after one, two, three, and four hours of high shear mixing. Large batch exfoliation of graphite into unsaturated polyester resin at 25% ( w/w) graphite loading

Unsaturated polyester resin (PCCR 741-6510 isophthalic base pultrusion resin, 4502 g) was added to a 12-liter capacity stainless steel mixing vessel equipped with an overhead open blade paddle stirrer with 4-inch diameter blade and a Silverson L5M overhead high shear mixer fitted with a 1.25-inch diameter mixing assembly and general purpose disintegrating mixing head. The mixing vessel was immersed in a water cooling batch containing a stainless steel cooling coil held at 0°C using a recirculating chiller. The resin was mixed with the paddle stirrer running at 500 rpm and the high shear mixer running at 6750 rpm, and graphite powder (Asbury A625 synthetic graphite, 1500 g) was added to the resin in three aliquots of 500 grams each at 20 minute intervals. Mixing time was measured from when the graphite addition was complete, and continued for 6 hours. Resin samples were removed at one-hour intervals throughout the mixing period. Co-exfoliation of graphite and multiwall carbon nanotubes into unsaturated polyester resin at 10% ( w/w) graphite loading and 0.5% ( w/w) m ultiwall carbon nanotubes loading Unsaturated polyester resin (PCCR 741-6510 isophthalic base pultrusion resin,

151.06 g) was added to an 8-ounce glass jar. Graphite powder (Asbury A625 synthetic graphite, 16.87 g) was mixed into the liquid resin by manual mixing until a uniformly mixed suspension was obtained. The glass jar was cooled at 5°C, and the suspension was then mixed using a Silverson L5M overhead high shear lab mixer fitted with a 1-inch tubular mixing assembly and general purpose disintegrating mixing head. The suspension was mixed at 8000 rpm for 1.75 hours. Then, multiwall carbon nanotubes (Nanocyl NC7000, 0.84 g) were added and mixing was continued for an additional 7 minutes. Throughout the mixing, the jar was continuously moved in relation to the mixing head to ensure mixing of the entire sample volume and thus minimize and/or eliminate "dead zones" in the mixture.

Preparation of cured samples for dynamic mechanical analysis and impact testing Benzoyl peroxide (Luperox A98, 0.8002 g) was soaked in styrene (ReagentPlus with 4- tert-butylcatechol as stabilizer, 1.65 g) for 10 minutes in a 100-mL glass beaker to provide a polymerizer. A graphene/unsaturated polyester resin prepared as described by one of the methods above (approximately 80.18 g) was then added to the polymerizer in the beaker and manually stirred until uniform. The mixture was poured into a silicon bar cavity mold (Ladd Research Industries, 12.5 cm x 1.2 cm cavities) treated with silicon mold release agent (Slide Products No. 40112N) to a depth of approximately 2 mm to provide polymer bars for dynamic mechanical analysis (DMA) and to a depth of approximately 3.25 mm to provide bars for Izod impact tests. The open top of the mold was then covered with a sheet of flat glass to prevent styrene evaporation and placed in an oven at 60°C. After incubating at 60°C for 15 hours, the temperature was increased at hourly intervals to 85°C, 95°C, 105°C, and 115°C. After incubating at 115°C for one hour, the mold was removed from the oven and allowed to cool to ambient ("room") termperature. The sample polymer bars were then removed from the mold and smoothed with sandpaper to remove surface imperfections. The smoothed polymer bars were then trimmed to a length of 6.25 cm for Izod impact testing or a length of 4.4 cm for DMA testing as necessary.

Exfoliation of graphite into epoxy resin at 30% (w/w) loading

Bis phenol A epoxy resin (Epon 828, 185.32 g) was added to an 8 ounce glass jar.

Graphite powder (Asbury A625 synthetic graphite, 79.42 g) was mixed into the liquid resin by manual mixing until a uniformly mixed suspension was obtained. The glass jar was placed in a cooling batch at 5 °C, and the suspension was then mixed using a Silverson L5M overhead high shear lab mixer fitted with a 1 inch tubular mixing assembly and low flow, high shear, mixing head. The mixing was carried out at 8,000 rpm for four hours. Throughout the mixing period, the jar was continuously moved in relation to the mixing head to ensure mixing of the entire sample volume (i.e. no "dead zones"). Samples of the mixture were removed before the high shear mixing was started (graphite control) and after each hour of high shear mixing.

Exfoliation of graphite into poly(vinylchloride) (PVC) resin at 30% (w/w) loading

PVC powder (Sigma Aldrich, Mw = 62,000, 12.59 g) was dissolved in 50.39 g of reagent grade THF in an 8 ounce glass jar by heating in a warm water bath with constant stirring. Graphite powder (Asbury A625 synthetic graphite, 5.40 g) was mixed into the viscous resin solution by manual mixing until a uniformly mixed suspension was obtained. The glass jar was placed in a cooling batch at 10 °C, and the suspension was then mixed using a Silverson L5M overhead high shear lab mixer fitted with a 1 inch tubular mixing assembly and low flow, high shear mixing head. The mixing was carried out at 8,000 rpm for two hours, moving the sample in relation to the mixing head every 20 minutes to ensure mixing of the entire sample volume (i.e. no "dead zones") resulting in a uniform, physically stable, dispersion which was poured into open cavity molds where the solvent was allowed to slowly evaporate at room temperature overnight followed by heating at 60 °C in a convection oven for one hour to produce test bars. Preparation of cured epoxy samples for dynamic mechanical analysis (DMA)

Epoxy resin samples were mixed with epoxy hardener (Dow DEH 20) in a weight ratio of 5 parts resin to 1 part hardener, poured into silicone cavity molds (Ladd Research Industries, 12.5 cm by 1.2 cm cavities) to a depth of about 2 mm, and cured in a vacuum oven at 60 °C for two hours to produce cured epoxy test bars for DMA. Example 1 - Dynamic mechanical analysis of cured unsaturated polyester resin samples

Cured sample polymer bars, prepared as describe above from the 10% and 20% graphite loading examples described above, were analyzed by dynamic mechanical analysis (DMA) using a constant temperature strain sweep at room temperature and a 3 -point bending mode. The storage modulus values as a function of mixing time for 10% graphite loading are summarized in Figure 1. For reference, storage modulus values were measured for controls. The first "unsheared resin" control was a cured polymer bar of the UPR resin with no added graphite and no high shear mixing treatment. The second "sheared resin" control was a cured polymer bar of the resin with no added graphite that was high shear mixed for a period of 24 hours.

As shown in Figure 1, the "sheared resin" samples showed a lower storage modulus than the "unsheared resin" samples. Figure 2 shows a similar result for the resin-only "Control" that was not high shear mixed and the "Sheared Control" that was high shear mixed. Without being bound by theory, these data may indicate that some resin properties degraded during the prolonged high shear mixing in the absence of graphite.

Next, the test samples with 10% graphite loading were evaluated and compared with the "unsheared resin" reference. No significant change in storage modulus relative to the "unsheared resin" control was observed for the "0 hour shear" sample (comprising 10% graphite and not high shear mixed) (Figure 1, columns 2 and 3). However, the data demonstrated a 12% increase in the storage modulus after 1 hour of high shear mixing with 10% graphite relative to the "unsheared resin" reference (Figure 1, columns 4 and 2). Further, the data demonstrated a 20% increase in the storage modulus after 2 hours of high shear mixing relative to the "unsheared resin" reference (Figure 1, columns 5 and 2). The storage modulus measured after 3 hours of high shear mixing showed only a 7% increase relative to the "unsheared resin" reference (Figure 1, columns 6 and 2) and was decreased with respect to the value measured after 2 hours (Figure 1, columns 6 and 5).

The storage modulus values as a function of mixing time for 20% graphite loading are summarized in Figure 2. The storage modulus measured for the "0 Hr" shear sample (comprising 20% graphite and not high shear mixed) was not significantly different than the storage modulus of the unsheared resin-only "Control" (Figure 2, columns 1 and 3). After 1 hour of high shear mixing with 20% graphite, the storage modulus of the 20% graphite samples ("1 Hr") increased by 22% relative to the unsheared resin-only "Control" (Figure 2, columns 4 and l). Continued high shear mixing for 2, 3, and 4 hours resulted in samples ("2 Hr", "3 Hr", and "4 Hr") having a measured storage modulus that was increased by 20%, 28%, and 31% respectively relative to the unsheared resin-only "Control" (Figure 2, columns 5 and V, columns 6 and V, columns 7 and l).

Example 2 - Izod impact testing of cured unsaturated polyester resin samples at 10% (w/w) graphite loading

Cured sample test bars were prepared as described above from unsheared resin containing no graphite! and from resin with 10% (w/w) graphite loading. Samples were high shear mixed as described above for 2.25 hours. Izod impact tests were carried out by Akron Rubber Development Laboratory Inc. according to ASTM method D 256- 10. The average Izod impact strength for 10 test bars made from the resin with 10% graphite loading was 0.222 ft-lbs/in (standard deviation = 0.028), which was 15% lower than the average of 0.261 ft-lbs/in (standard deviation = 0.013) for 8 test bars made from unsheared resin containing no graphite. However, the difference in averages is less than the sum of the standard deviations, so the difference is not statistically significant.

Example 3 - Electrical resistivity testing of cured unsaturated polyester resin samples Cured sample test bars were prepared as described above from unsheared resin containing no graphite! and from resin with 10% graphite loading and 0.5% MWCNT loading as described above. The test bars were tested for electrical resistivity using a Static Solutions RT- 1000 Megohmmeter. The average resistivity value for the unsheared resin-only test bars was 6.76 x 10¹⁰ Ohm-cm and the average resistivity value for the test bars with 10% graphite and 0.5% MWCNT was 2.46 x 10⁷ Ohm-cm. The value of

6.76 x 10¹⁰ Ohm-cm measured for the unsheared resin-only test bars is characteristic of a highly insulating material. In contrast, the value of 2.46 x 10⁷ Ohm-cm measured for the test bars with 10% graphite and 0.5% MWCNT is within the range considered effective for electrostatic dissipation.

Example 4 - Dynamic mechanical analysis of cured unsaturated polyester samples from large batch mixing

The storage modulus values as a function of mixing time for 25% graphite loading are summarized in Figure 3. After 1 hour of high shear mixing, there was a 22% increase in storage modulus versus the unsheared resin-only reference. Continued high shear mixing for 2, 3, 4, 5, and 6 hours resulted in storage modulus increases of 23%, 16%, 29%, 29%, and 15%, respectively versus the unsheared resin only reference.

Example 5 - Dynamic mechanical analysis of cured epoxy samples

Cured epoxy test bars, prepared as described in the Materials and Methods above, were analyzed by dynamic mechanical analysis (DMA) on an RSA III Dynamic Mechanical Analyzer using a constant temperature strain sweep at room temperature and 3 -point bending mode. The storage modulus values as a function of time for 30% graphite loading are summarized in Figure 4. The storage modulus measured for the "0 hr" samle (comprising 30% graphite and not high shear mixed) was 11% higher than the epoxy resin-only control. After 1 hour of high shear mixing there was an increase in storage modulus to 14% higher than the resin-only control. After 2 hours of high shear mixing there was a further increase in storage modulus to a value 27% higher than the resin- only control. After 3 and 4 hours of mixing there was a decrease in storage modulus to values that were 22% and 17% higher than the control, respectively.

All publications and patents mentioned in the above specification are herein incorporated by reference in their entirety for all purposes. Various modifications and variations of the described compositions, methods, and uses of the technology will be apparent to those skilled in the art without departing from the scope and spirit of the technology as described. Although the technology has been described in connection with specific exemplary embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various

modifications of the described modes for carrying out the invention that are obvious to those skilled in the art are intended to be within the scope of the following claims.

Claims

CLAIMS WE CLAIM:

1. A method of producing a graphene suspension in a resin, the method comprising high shear mixing a mixture of resin and graphite to produce a graphene suspension in a resin.

2. The method of claim 1 wherein the mixture of resin and graphite comprises at least 1% graphite (w/w).

3. The method of claim 1 wherein the mixture of resin and graphite comprises at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, or 40% graphite (w/w).

4. The method of claim 1 wherein the graphene suspension in the resin comprises at least 0.1% graphene (w/w).

5. The method of claim 1 wherein the graphene suspension in the resin comprises at least 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, or more graphene (w/w).

6. The method of claim 1 wherein the resin is a liquid thermoset resin.

7. The method of claim 1 wherein the resin is a liquefied thermoplastic resin.

8. The method of claim 1 wherein the graphene suspension in the resin comprises unexfoliated graphite particles having a size that minimizes and/or eliminates undesirable mechanical characteristics.

9. The method of claim 1 wherein the graphene suspension in the resin is

exfoliation solvent-free, preferably completely free of any added exfoliation solvents.

10. The method of claim 1 wherein the mixture of resin and graphite is high shear mixed for at least 30 minutes.

11. The method of claim 1 wherein the mixture of resin and graphite is high shear mixed for at least 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours.

12. The method of claim 1 wherein the mixture of resin and graphite is high shear mixed using a stator-rotor mixer wherein the shear gap is between 50 μηι and 150 μηι and the tip speed of the rotor is at least 400 feet/second, at least 500 feet/second, at least 600 feet/second, at least 700 feet/second, or at least 800 feet/second, or more.

13. A method of producing a polymer- graphene composite material, the method comprising:

a) high shear mixing a mixture of resin and graphite to produce a graphene suspension in a resin! and

b) curing the graphene suspension in the resin to produce a polymer- graphene composite material.

14. The method of claim 13 wherein the mixture of resin and graphite comprises at least 1% graphite (w/w).

15. The method of claim 13 wherein the mixture of resin and graphite comprises at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, or 40% graphite (w/w).

16. The method of claim 13 wherein the graphene suspension in the resin comprises at least 0.1% graphene (w/w).

17. The method of claim 13 wherein the graphene suspension in the resin comprises at least 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, or more graphene (w/w).

18. The method of claim 13 wherein the resin is a liquid thermoset resin.

19. The method of claim 13 wherein the resin is a liquefied thermoplastic resin.

20. The method of claim 13 wherein the graphene suspension in the resin comprises unexfoliated graphite particles having a size that minimizes and/or eliminates undesirable mechanical characteristics of the polymer- gra he ne composite material.

The method of claim 13 wherein the graphene suspension in the resin is exfoliation solvent-free, preferably completely free of any added exfoliation solvents.

The method of claim 13 wherein the mixture of resin and graphite is high shear mixed for at least 30 minutes.

The method of claim 13 wherein the mixture of resin and graphite is high shear mixed for at least 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours.

The method of claim 13 wherein the mixture of resin and graphite is high shear mixed using a stator-rotor mixer wherein the shear gap is between 50 μηι and 150 μηι and the tip speed of the rotor is at least 400 feet/second, at least 500 feet/second, at least 600 feet/second, at least 700 feet/second, or at least 800 feet/second, or more.

The method of claim 13 wherein the polymer- graphene composite material comprises at least 0.1% graphene (w/w).

The method of claim 13 wherein the polymer- graphene composite material comprises at least 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, or more graphene (w/w).

The method of claim 13 wherein the polymer- graphene composite material comprises unexfoliated graphite particles having a size that minimizes and/or eliminates undesirable mechanical characteristics of the polymer- graphene composite material.

The method of claim 13 wherein the polymer- graphene composite material is exfoliation solvent-free, preferably completely free of any added exfoliation solvents.

29. A method of producing a polymer- graphene composite material, the method comprising:

a) high shear mixing a mixture of resin, graphite, and multiwall carbon nanotubes to produce a suspension of graphene and exfoliated multiwall carbon nanotubes in a resin! and

b) curing the suspension of graphene and exfoliated multiwall carbon

nanotubes in a resin to produce a polymer- graphene composite material.

30. The method of claim 29 wherein the mixture of resin, graphite, and multiwall carbon nanotubes comprises at least 1% graphite (w/w) and at least 0.1% multiwall carbon nanotubes (w/w).

31. A method of producing a polymer- graphene composite material, the method

comprising:

a) high shear mixing a mixture of resin and graphite to produce a suspension of graphene in a resin!

b) adding multiwall carbon nanotubes to the suspension of graphene in a resin to produce a suspension of graphene and multiwall carbon nanotubes in a resin!

c) high shear mixing the suspension of graphene and multiwall carbon

nanotubes in a resin to produce a suspension of graphene and exfoliated multiwall carbon nanotubes! and

d) curing the suspension of graphene and exfoliated multiwall carbon

nanotubes in a resin to produce a polymer- graphene composite material.

32. The method of claim 31 wherein the mixture of resin and graphite comprises at least 1% graphite (w/w) and the suspension of graphene and exfoliated multiwall carbon nanotubes comprises at least 0.1% multiwall carbon nanotubes (w/w).

33. The method of claim 31 further comprising:

adding multiwall carbon nanotubes to the graphene suspension in a resin to produce a suspension of graphene and multiwall carbon nanotubes in a resin! and high shear mixing the suspension of graphene and multiwall carbon nanotubes in the resin to produce a suspension of graphene and exfoliated multiwall carbon nanotubes in the resin.

34. A polymer-graphene composite material produced by a method comprising high shear mixing a mixture of resin and graphite to produce a graphene suspension in a resin.

35. The polymer-graphene composite material of claim 34 wherein the polymer- graphene composite material is an exfoliation solvent-free polymer-graphene composite material, preferably a polymer-graphene composite material that is completely free of any added exfoliation solvents.

36. A composition comprising a resin and graphene produced by a method comprising high shear mixing a mixture of resin and graphite to produce a graphene suspension in a resin.

37. The composition comprising a resin and graphene of claim 36 wherein the

composition comprising a resin and graphene is an exfoliation-free composition comprising a resin and graphene, preferably a composition comprising a resin and graphene that is completely free of any added exfoliation solvents.

38. An exfoliation solvent-free composition comprising a resin and at least 0.1%

graphene (w/w).

39. An exfoliation solvent-free composition comprising a resin, at least 0.1%

graphene (w/w), and at least 0.1% exfoliated multiwall carbon nanotubes (w/w).

40. The exfoliation solvent-free composition of any one of claims 38 or 39 wherein the composition is an exfoliation solvent-free polymer-graphene composite material.

41. A composition comprising a resin and at least 0.1% graphene (w/w) that is

completely free of any added exfoliation solvents.

42. A composition comprising a resin, at least 1% graphene (w/w), and at least 0.1% exfoliated multiwall carbon nanotubes (w/w) that is completely free of any added exfoliation solvents.

A system for producing a polymer- graphene composite material, the system comprising a resin, graphite, a high shear mixer, and a curing agent.

The system of claim 41 wherein the resin is a liquid thermoset resin.

The system of claim 43 wherein the resin is a liquefied thermoplastic resin.

The system of claim 43 wherein the curing agent is a chemical curing agent.

47. The system of claim 43 further comprising multiwall carbon nanotubes.