WO2014168979A1

WO2014168979A1 - Use of graphene-containing polymer composites

Info

Publication number: WO2014168979A1
Application number: PCT/US2014/033383
Authority: WO
Inventors: Robert Heuser; Jeffrey KACZMARCZYK; John S. Lettow
Original assignee: Vorbeck Materials
Priority date: 2013-04-08
Filing date: 2014-04-08
Publication date: 2014-10-16

Abstract

Method of using a article comprising heating the article to a temperature of at least about 150 °C, wherein the article comprises a composition comprising at least one polymer and graphene sheets. Also disclosed are a method of using an article, wherein the article comprises a first composition comprising at least one polymer, graphene sheets, and, optionally, additional components, comprising heating the article to a temperature above which a second composition that is identical to the first composition except that it has no graphene sheets has a storage modulus that is at least about 10 percent less than the storage modulus of the second composition at 25 °C, or heating the article to a temperature that is at about or greater than the heat deflection temperature of a second composition that is identical to the first composition except that it has no graphene sheets.

Description

USE OF GRAPHENE-CONTAINING POLYMER COMPOSITES

Reference to Related Applications

The present application claims priority to U.S. Provisional Application

61/809,453, filed on April 8, 2013, the entire contents of which is hereby incorporated by reference.

Field of the Invention

The use of articles comprising at least one polymer and graphene sheets at elevated temperatures.

Background

Articles made from polymer compositions are used in many areas. In some cases, uses are limited by temperature limitations of the of polymer compositions (for example, some compositions can have exhibit diminished physical properties at higher temperatures). In some cases, it can be useful or necessary to use polymer systems that are more costly for higher temperature applications. It may also be desirable to replace metal components with polymer compositions, but in applications require resistance to elevated temperatures, this may not be cost-effective or even possible.

Summary of the Invention

Disclosed and claimed herein is a method of using an article, comprising heating the article to a temperature of at least about 100 °C, wherein the article comprises a composition comprising at least one polymer and graphene sheets. Further disclosed and claimed is method of using an article, wherein the article comprises a first composition comprising at least one polymer, graphene sheets, and, optionally, additional components, comprising heating the article to a temperature above which a second composition that is identical to the first composition except that it has no graphene sheets has a storage modulus that is at least about 10 percent less than the storage modulus of the second composition at 25 °C. Also disclosed and claimed is a method of using an article, wherein the article comprises a first composition comprising at least one polymer, graphene sheets, and, optionally, additional components, comprising heating the article to a temperature that is at about or greater than the heat deflection temperature of a second composition that is identical to the first composition except that it has no graphene sheets.

Detailed Description of the Invention

The composites comprise a composition comprising at least one polymer and graphene sheets. The graphene sheets are dispersed in the polymer matrix. The composites can further comprise additional components. Composites comprising graphene sheets are referred to herein as "filled compositions". A material having the same composition as filled composite (i.e. comprising the polymer(s) and other components), except for the graphene sheets is referred to herein as the filled composite's equivalent "unfilled composition". The "unfilled compositions" may have additional components.

The composites are formed into articles that are used at elevated temperatures. The articles may be part of a larger apparatus. Some or all of the larger apparatus can be exposed to elevated temperatures during use.

By "use" is meant the use of the article in practical manner. The mere act of performing analytical/laboratory testing of properties of the composite material or articles made therefrom at elevated temperatures is not considered to be a use, for example.

During use the article is exposed to elevated temperatures for a consecutive time of at least about 1 second, or at least about 30 seconds, or at least about 1 minute, or at least about 5 minutes, or at least about 10 minutes, or at least about 30 minutes, or at least about 1 hours, or at least about 5 hours, or at least about 10 hours, or at least about 1 day, or at least about 5 days, or at least about 10 days, or at least about 30 days, or at least about 100 days, or at least about 1 year, or at least about 3 years, or at least about 5 years.

The elevated temperatures can be at least about 100 °C, or at least about 125 °C, or at least about 150 °C, or at least about 160 °C, or least about 170 °C, or at least about 180 °C, or at least about 190 °C, or at least about 200 °C, or at least about 220 °C, or at least about 240 °C, or at least about 260 °C, or at least about 280 °C, or at least about 300 °C, or at least about 320 °C, or at least about 340 °C, or at least about 360 °C, or at least about 380 °C, or at least about 400 °C, or at least about 420 °C, or at least about 440 °C, or at least about 460 °C, or at least about 480 °C, or at least about 500 °C, or at least about 520 °C, or at least about 540 °C, or at least about 560 °C, or at least about 580 °C, or at least about 600 °C. In some cases, the article is used at a temperature above which the corresponding unfilled composition has a storage modulus that is at least about 10 percent less than the storage modulus it has at 25 °C, or at least about 20 percent less than the storage modulus it has at 25 °C, or at least about 30 percent less than the storage modulus it has at 25 °C, or at least about 40 percent less than the storage modulus it has at 25 °C, or at least about 50 percent less than the storage modulus it has at 25 °C, or at least about 60 percent less than the storage modulus it has at 25 °C.

Storage modulus can be measured using a dynamic mechanical analyzer. For example, it can be measured using a multifrequency strain method with a tension clamp.

In some cases, the article is used at a temperature that is at about the heat deflection temperature of the unfilled composition, or at least 5 °C above, or at least about 10 °C above, or at least about 15 °C above, or at least about 20 °C above, or at least about 25 °C above, or at least about 30 °C above, or at least about 40 °C above, or at least about 50 °C above, or at least about 60 °C above, or at least about 70 °C above, or at least about 80 °C above, or at least about 90 °C above, or at least about 100 °C above, or at least about 120 °C above, or at least about 140 °C above, or at least about 160 °C above, or at least about 180 °C above, or at least about 200 °C above, or at least about 220 °C above, or at least about 240 °C above, or at least about 260 °C above, or at least about 280 °C above, or at least about 300 °C above the heat deflection temperature of the unfilled temperature. Heat deflection temperatures can be

determined using ASTM D648 at a load of 0.45 or 1.8 MPa.

The polymers can be thermosets, thermoplastics, non-melt processible polymers, rubbers, elastomers, thermoplastic elastomers, polymer alloys, copolymers (where the term "copolymers" refers to polymers derived from two or more monomers), etc. The polymers can be crosslinked, vulcanized, or otherwise cured.

Examples of polymers include polyolefins, such as polyethylene, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density

polyethylene, ultrahigh molecular weight polyethylene, polypropylene, olefin polymers and copolymers, ethylene/propylene copolymers (EPR), ethylene/propylene/diene monomer copolymers (EPDM); olefin and styrene copolymers; polystyrene (including high impact polystyrene); styrene/butadiene rubbers (SBR);

styrene/ethylene/butadiene/styrene copolymers (SEBS); isobutylene/maleic anhydride copolymers; ethylene/acrylic acid copolymers; acrylonitrile/butadiene/styrene

copolymers (ABS); styrene/acrylonitrile polymers (SAN); styrene/maleic anhydride copolymers; poly(acrylonitrile); polyethylene/acrylonitrile butadiene styrene (PE/ABS), polyvinyl pyrrolidone) and polyvinyl pyrrolidone) copolymers; vinyl acetate/vinyl pyrrolidone copolymers; polyvinyl acetate); polyvinyl acetate) copolymers;

ethylene/vinyl acetate copolymers (EVA); polyvinyl alcohols) (PVOH); ethylene/vinyl alcohol copolymers (EVOH); polyvinyl butyral) (PVB); polyvinyl formal), polycarbonates (PC); polycarbonate/acrylonitrile butadiene styrene copolymers (PC/ABS); polyamides; polyesters; liquid crystalline polymers (LCPs); poly(lactic acid) (PLA); poly(phenylene oxide) (PPO); PPO-polyamide alloys; polysulphones (PSU); polysulfides; poly(phenylene sulfide); polyetherketone (PEK); polyetheretherketone (PEEK); cross-linked

polyetheretherketone (XPEEK); polyimides; polyoxymethylene (POM) homo- and copolymers (also called polyacetals); polyetherimides; polyphenylene (self-reinforced polyphenylene (SRP); polybenimidazole (PBI), aramides (such as Kevlar® and

Nomex®); polyureas; alkyds; cellulosic polymers (such as nitrocellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose, cellulose acetate, cellulose acetate propionates, and cellulose acetate butyrates); polyethers (such as poly(ethylene oxide), poly(propylene oxide), poly(propylene glycol), oxide/propylene oxide copolymers, etc.); alkyds; acrylic latex polymers; polyester acrylate oligomers and polymers;

polyester diol diacrylate polymers; phenolic resins; melamine formaldehyde resins; urea formaldehyde resins; novolacs; polyvinyl chloride); poly(vinylidene chloride);

fluoropolymers (such as polytetrafluoroethylene (PTFE), fluorinated ethylene propylene polymers (FEP), polyvinyl fluoride), poly(vinylidene fluoride), vinylidene

fluoride/hexafluoropropylene copolymers (VF2/HFP), vinylidene fluoride/

hexafluoropropylene/tetrafluoroethylene (VF2/HFP/TFE) copolymers, vinylidene fluoride)/vinyl methyl ether/tetrafluoroethylene (VF2/PVME/TFE) copolymers, vinylidene fluoride/hexafluoropropylene/tetrafluoroethylene copolymers (VF2/HPF/TFE), vinylidene fluoride/tetrafluoroethylene/propylene (VF2/TFE/P) copolymers, perfluoroelastomers such as tetrafluoroethylene perfluoroelastomers (FFKM), highly fluorinated elastomers (FEPM), perfluoro(alkyl vinyl ethers), perfluoro(methyl vinyl ether) (PMVE),

perfluoro(ethyl vinyl ether) (PEVE), perfluoro(propyl vinyl ether) (PPVE), fluoropolymers having one or more repeat units derived from vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene, chlorotrifluoroethylene (CTFE), perfluoro(alkyl vinyl ethers), etc.); polysiloxanes (e.g., (polydimethylenesiloxane, dimethylsiloxane/vinylmethylsiloxane copolymers, vinyldimethylsiloxane terminated poly(dimethylsiloxane), etc.);

polyurethanes (thermoplastic and thermosetting (including crosslinked polyurethanes such as those crosslinked amines, etc.); epoxy polymers (including crosslinked epoxy polymers such as those crosslinked with polysulfones, amines, etc.); acrylate polymers (such as poly(methyl methacrylate), acrylate polymers and copolymers, methyl methacrylate polymers, methacrylate copolymers,

polymers derived from one or more acrylates, methacrylates, ethyl acrylates, ethyl methacrylates, butyl acrylates, butyl methacrylates, glycidyl acrylates and methacrylates, etc.), etc.

Examples of polyamides include, but are not limited to, aliphatic polyamides (such as polyamide 4,6; polyamide 6,6; polyamide 6; polyamide 1 1 ; polyamide 12;

polyamide 6,9; polyamide 6,10; polyamide 6,12; polyamide 10,10; polyamide 10,12; and polyamide 12,12), alicyclic polyamides, and aromatic polyamides (such as poly(m- xylylene adipamide) (polyamide MXD,6)) and polyterephthalamides such as

poly(dodecamethylene terephthalamide) (polyamide 12,T), poly(decamethylene terephthalamide) (polyamide 10,T), poly(nonamethylene terephthalamide) (polyamide 9,T), the polyamide of hexamethylene terephthalamide and hexamethylene adipamide, the polyamide of hexamethyleneterephthalamide, and 2- methylpentamethyleneterephthalamide), etc. The polyamides can be polymers and copolymers (i.e., polyamides having at least two different repeat units) having melting points between about 120 and 255 °C including aliphatic copolyamides having a melting point of about 230 °C or less, aliphatic copolyamides having a melting point of about 210 °C or less, aliphatic copolyamides having a melting point of about 200 °C or less, aliphatic copolyamides having a melting point of about 180 °C or less, etc. Examples of these include those sold under the trade names Macromelt by Henkel and Versamid by Cognis.

Examples of acrylate polymers include those made by the polymerization of one or more acrylic acids (including acrylic acid, methacrylic acid, etc.) and their derivatives, such as esters. Examples include methyl acrylate polymers, methyl methacrylate polymers, and methacrylate copolymers. Examples include polymers derived from one or more acrylates, methacrylates, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, glycidyl acrylate, glycidyl methacrylates, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, hydroxyethyl acrylate, hydroxyethyl (meth)acrylate, acrylonitrile, and the like. The polymers can comprise repeat units derived from other monomers such as olefins (e.g. ethylene, propylene, etc.), vinyl acetates, vinyl alcohols, vinyl pyrrolidones, etc. They can include partially neutralized acrylate polymers and copolymers (such as ionomer resins).

Examples of polyesters include, but are not limited to, poly(butylene

terephthalate) (PBT), poly(ethylene terephthalate) (PET), poly(1 ,3-propylene

terephthalate) (PPT), poly(ethylene naphthalate) (PEN), poly(cyclohexanedimethanol terephthalate) (PCT)), etc.

Examples of rubbers and elastomers include styrene/butadiene copolymers (SBR), styrene/ethylene/butadiene/styrene copolymer (SEBS), polyisoprene,

ethylene/propylene copolymers (EPR), ethylene/propylene/monomer copolymers (EPM), ethylene/propylene/diene monomer copolymers (EPDM), chlorosulphonated

polyethylene (CSM), chlorinated polyethylene (CM), ethylene/vinyl acetate copolymers (EVM), butyl rubber, natural rubber, polybutadiene (Buna CB), chloroprene rubber (CR), halogenated butyl rubber, bromobutyl rubber, chlorobutyl rubber, nitrile rubber

(butadiene/acrylonitrile copolymer) (NBR) (Buna N rubber), hydrogenated nitrile rubber (HNBR), carboxylated high-acrylonitrile butadiene rubbers (XNBR), carboxylated HNBR, epichlorohydrin copolymers (ECO), epichlorohydrin terpolymers (GECO), polyacrylic rubber (ACM, ABR), ethylene/acrylate rubber (AEM), polynorbornenes, polysulfide rubbers (e.g. OT and EOT), copolyetheresters, ionomers, polyurethanes, polyether urethanes, polyester urethanes, silicone rubbers and elastomers (such as polysiloxanes (e.g., (polydimethylenesiloxane, dimethylsiloxane/vinylmethylsiloxane copolymers, vinyldimethylsiloxane terminated poly(dimethylsiloxane), etc.), fluorosilicone rubber, fluoromethyl silicone rubber (FMQ), fluorovinyl silicone rubbers (FVMQ), phenylmethyl silicone rubbers (PMQ), vinyl silicone rubbers, etc.), fluoropolymers (such as

perfluorocarbon rubbers (FFKM), fluoronated hydrocarbon rubbers (FKM), fluorinated ethylene propylene polymers (FEP), polyvinyl fluoride), poly(vinylidene fluoride), vinylidene fluoride/hexafluoropropylene copolymers (VF2/HFP), vinylidene fluoride/ hexafluoropropylene/tetrafluoroethylene (VF2/HFP/TFE) copolymers, vinylidene fluoride)/vinyl methyl ether/tetrafluoroethylene (VF2/PVME/TFE) copolymers, vinylidene fluoride/hexafluoropropylene/tetrafluoroethylene copolymers (VF2/HPF/TFE), vinylidene fluoride/tetrafluoroethylene/propylene (VF2/TFE/P) copolymers, perfluoroelastomers such as tetrafluoroethylene perfluoroelastomers (FFKM), highly fluorinated elastomers (FEPM), perfluoro(alkyl vinyl ethers), perfluoro(methyl vinyl ether) (PMVE),

perfluoro(ethyl vinyl ether) (PEVE), perfluoro(propyl vinyl ether) (PPVE), fluoropolymers having one or more repeat units derived from vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene, chlorotrifluoroethylene (CTFE), perfluoro(alkyl vinyl ethers), etc.), and the like.

The polymers, graphene sheets, and other components, if used, can be formed into the composite compositions using any suitable means, including melt processing (using, for example, one or more of single or twin-screw extruders, blenders, kneaders, mixers, Brabender mixers, Banbury mixers, roller mills (such as two-roll mills, three-roll mill), etc.), solution/dispersion processing/blending, via thermosetting lay-ups, etc.

Some or all of the graphene sheets (and/or other components) can be added to monomer or oligomers that are then in-situ polymerized to form the polymers. The graphene sheets (and/or other components) can be added to a polymer matrix that is then cross-linked, vulcanized, or otherwise cured. Graphene sheets can be blended with rubbers and other elastomers in a mixer and the rubber or elastomer blends later crosslinked.

The graphene sheets can be added to the polymer as dry powder, in a solvent dispersion, suspension, or paste, or the like.

Articles can be formed from the composite compositions using any suitable method, including compression molding, extrusion, ram extrusion, injection molding, extrusion, co-extrusion, rotational molding, blow molding, injection blow molding, flexible molding, thermoforming, vacuum forming, casting, solution casting, centrifugal casting, overmolding, reaction injection molding, vacuum assisted resin transfer molding, spinning, printing, spraying, sputtering, coating, roll-to-roll processing, laminating, etc. Thermoset compositions can be formed by mixing resin precursors with graphene sheets and, optionally, other additives in a mold and curing to form the article.

Examples of other additives include accelerators, antioxidants, antiozonants, carbon black, calcium, clays, curing systems (e.g., peroxides (e.g., dicumyl peroxide), sulfur, initiators, etc.), crosslinkers, lubricants, mold-release agents, fatty acids (stearic acid), zinc oxide, silica, processing aids, blowing aids, adhesion promoters, plasticizers, dyes, pigments, reinforcing agents and fillers (glass fibers, carbon fibers, miners, etc.), heat stabilizers, UV stabilizers, flame retardants, metals, electrically and/or thermally conductive additives, etc.

The compositions can contain electrically conductive components, such as metals (including metal alloys), conductive metal oxides, conductive carbons, polymers, metal-coated materials, etc. These components can take a variety of forms, including particles, powders, flakes, foils, needles, etc. Examples of metals include, but are not limited to zinc, aluminum, nickel, silver, copper, tin, iron, gold, brass, bronze, platinum, palladium, lead, steel, rhodium, titanium, tungsten, magnesium, colloidal metals, etc.

Examples of metal oxides include antimony tin oxide and indium tin oxide and materials such as fillers coated with metal oxides. Metal and metal-oxide coated materials include, but are not limited to metal coated carbon and graphite fibers, metal coated glass fibers, metal coated glass beads, metal coated ceramic materials (such as beads), etc. These materials can be coated with a variety of metals, including nickel.

Examples of conductive carbons include, but are not limited to, graphite

(including natural, Kish, and synthetic, annealed, pyrolytic, highly oriented pyrolytic, etc. graphites), graphitized carbon, carbon black, carbon fibers and fibrils, carbon whiskers, vapor-grown carbon nanofibers, metal coated carbon fibers, carbon nanotubes

(including single- and multi-walled nanotubes), fullerenes, activated carbon, carbon fibers, expanded graphite, expandable graphite, graphite oxide, hollow carbon spheres, carbon foams, etc.

Examples of thermally conductive additives include metal oxides, nitrides, ceramics, minerals, silicates, etc. Examples include boron nitride, aluminum nitride, alumina, aluminum nitride, berylium oxide, nickel oxide, titanium dioxide, copper(l) oxide, copper (II) oxide, iron(ll) oxide, iron(l,ll) oxide (magnetite), iron (III) oxide, silicon dioxide, zinc oxide, magnesium oxide (MgO), etc.

Examples of curing and crosslinking agents include radical initiators such as radical polymerization initiators, radical sources, etc., including organic and inorganic compounds. Coagents and crosslinking promoters may be used as well. Examples include organic and inorganic peroxides (such as hydrogen peroxide, dialkyl peroxides, hydroperoxides, peracids, diacyl peroxides, peroxy esters, ketone peroxides,

hydrocarbon peroxides, organometallic peroxides, organic polyoxides, organic polyoxides, dialkyl trioxides, hydrotrioxides, tetroxides, alkali metal peroxides (such as lithium peroxide), etc.), azo compounds, polyphenylhydrocarbons, substituted

hydrazines, alkoxyamines, nitrocompounds, nitrates, nitrites, nitroxides, disulfides, polysulfides, persulfates (e.g. potassium persulfate, etc.), etc.

Examples of peroxides include, but are not limited to dibenzoyl peroxide, dicumyl peroxide, acetone peroxide, methyl ethyl ketone peroxide, lauroyl peroxide, fe/f-butyl peroxide, ie f-butyl peracetate, di-fe/f-amyl peroxide, ie f-butyl hydroperoxide, cumene hydroperoxide, 1 ,3-b/^'s-(ie f-butylperoxy-1 -propyl) benzene, b/^'s-(ie f-butylperoxy) valerate, b/^'s-(2,4-dichlorobenzoyl) peroxide, etc.

Examples of azo compounds include azobisisobutylonitrile (AIBN); 1 ,1 '- azobis(cyclohexanecarbonitrile) (ABCN); 2,2'-azobis(2-methylbutyronitrile); 2,2'- azobis(2-methylpropionitrile); 2,2'-azobis(2-methylpropionitrile); /V-ie f-butyl-/V-(2-methyl- 1 -phenylpropyl)-0-(1-phenylethyl)hydroxylamine, etc.

Graphite is made up of many layers of graphene, which are one-atom thick sheets of carbon atoms arranged in a hexagonal lattice. The graphene sheets are graphite sheets preferably having one or more layers of graphene having a surface area of from about 100 to about 2630 m²/g. In some embodiments, the graphene sheets primarily, almost completely, or completely comprise fully exfoliated single sheets of graphite (these are approximately < 1 nm thick and are often referred to as "graphene"), while in other embodiments, at least a portion of the graphene sheets can comprise partially exfoliated graphite sheets, in which two or more sheets of graphite have not been exfoliated from each other. The graphene sheets can comprise mixtures of fully and partially exfoliated graphite sheets. Graphene sheets are distinct from carbon nanotubes. Graphene sheets can have a "platy" (e.g. two-dimensional) structure and do not have the needle-like form of carbon nanotubes. The two longest dimensions of the graphene sheets can each be at least about 10 times greater, or at least about 50 times greater, or at least about 100 times greater, or at least about 1000 times greater, or at least about 5000 times greater, or at least about 10,000 times greater than the shortest dimension (i.e. thickness) of the sheets. Graphene sheets are distinct from expanded, exfoliated, vermicular, etc. graphite, which has a layered or stacked structure in which the layers are not separated from each other.

Graphene sheets may be made using any suitable method. For example, they may be obtained from graphite, graphite oxide, expandable graphite, expanded graphite, etc.. They may be obtained by the physical exfoliation of graphite, by for example, peeling, grinding, milling, graphene sheets. They made be made by sonication of precursors such as graphite. They may be made by opening carbon nanotubes. They may be made from inorganic precursors, such as silicon carbide. They may be made by chemical vapor deposition (such as by reacting a methane and hydrogen on a metal surface). They may be made by epitaxial growth on substrates such as silicon carbide and metal substrates and by growth from metal-carbon melts. They made by made They may be may by the reduction of an alcohol, such ethanol, with a metal (such as an alkali metal like sodium) and the subsequent pyrolysis of the alkoxide product (such a method is reported in Nature Nanotechnology (2009), 4, 30-33). They may be made from small molecule precursors such as carbon dioxide, alcohols (such as ethanol, methanol, etc.), alkoxides (such as ethoxides, methoxides, etc., including sodium, potassium, and other alkoxides). They may be made by the exfoliation of graphite in dispersions or exfoliation of graphite oxide in dispersions and the subsequently reducing the exfoliated graphite oxide. Graphene sheets may be made by the exfoliation of expandable graphite, followed by intercalation, and ultrasonication or other means of separating the intercalated sheets (see, for example, Nature Nanotechnology (2008), 3, 538-542). They may be made by the intercalation of graphite and the subsequent exfoliation of the product in suspension, thermally, etc. Exfoliation processes may be thermal, and include exfoliation by rapid heating, using microwaves, furnaces, hot baths, etc.

Graphene sheets can be made from graphite oxide (also known as graphitic acid or graphene oxide). Graphite can be treated with oxidizing and/or intercalating agents and exfoliated. Graphite can also be treated with intercalating agents and

electrochemically oxidized and exfoliated. Graphene sheets can be formed by ultrasonically exfoliating suspensions of graphite and/or graphite oxide in a liquid (which can contain surfactants and/or intercalants). Exfoliated graphite oxide dispersions or suspensions can be subsequently reduced to graphene sheets. Graphene sheets can also be formed by mechanical treatment (such as grinding or milling) to exfoliate graphite or graphite oxide (which would subsequently be reduced to graphene sheets).

Reduction of graphite oxide to graphene can be by means of chemical reduction and can be carried out on graphite oxide in a dry form, in a dispersion, etc.. Examples of useful chemical reducing agents include, but are not limited to, hydrazines (such as hydrazine, Λ/,/V-dimethylhydrazine, etc.), sodium borohydride, citric acid, hydroquinone, isocyanates (such as phenyl isocyanate), hydrogen, hydrogen plasma, etc.. A dispersion or suspension of exfoliated graphite oxide in a carrier (such as water, organic solvents, or a mixture of solvents) can be made using any suitable method (such as ultrasonication and/or mechanical grinding or milling) and reduced to graphene sheets.

Graphite oxide can be produced by any method known in the art, such as by a process that involves oxidation of graphite using one or more chemical oxidizing agents and, optionally, intercalating agents such as sulfuric acid. Examples of oxidizing agents include nitric acid, nitrates (such as sodium and potassium nitrates), perchlorates, potassium chlorate, sodium chlorate, chromic acid, potassium chromate, sodium chromate, potassium dichromate, sodium dichromate, hydrogen peroxide, sodium and potassium permanganates, phosphoric acid (H₃P0₄), phosphorus pentoxide, bisulfites, etc. Preferred oxidants include KCI0₄; HN0₃ and KCI0₃; KMn0₄ and/or NaMn0₄;

KMn0₄ and NaN0₃; K₂S₂0₈ and P₂0₅ and KMn0₄; KMn0₄ and HN0₃; and HN0₃.

Preferred intercalation agents include sulfuric acid. Graphite can also be treated with intercalating agents and electrochemically oxidized. Examples of methods of making graphite oxide include those described by Staudenmaier (Ber. Stsch. Chem. Ges.

(1898), 31, 1481 ) and Hummers (J. Am. Chem. Soc. (1958), 80, 1339).

One example of a method for the preparation of graphene sheets is to oxidize graphite to graphite oxide, which is then thermally exfoliated to form graphene sheets (also known as thermally exfoliated graphite oxide), as described in US 2007/0092432, the disclosure of which is hereby incorporated herein by reference. The thusly formed graphene sheets can display little or no signature corresponding to graphite or graphite oxide in their X-ray diffraction pattern.

The thermal exfoliation can be carried out in a continuous, semi-continuous batch, etc. process.

Heating can be done in a batch process or a continuous process and can be done under a variety of atmospheres, including inert and reducing atmospheres (such as nitrogen, argon, and/or hydrogen atmospheres). Heating times can range from under a few seconds or several hours or more, depending on the temperatures used and the characteristics desired in the final thermally exfoliated graphite oxide. Heating can be done in any appropriate vessel, such as a fused silica, mineral, metal, carbon (such as graphite), ceramic, etc. vessel. Heating can be done using a flash lamp or with microwaves. During heating, the graphite oxide can be contained in an essentially constant location in single batch reaction vessel, or can be transported through one or more vessels during the reaction in a continuous or batch mode. Heating can be done using any suitable means, including the use of furnaces and infrared heaters.

Examples of temperatures at which the thermal exfoliation and/or reduction of graphite oxide can be carried out are at least about 150 °C, at least about 200 °C, at least about 300 °C, at least about 400 °C, at least about 450 °C, at least about 500 °C, at least about 600 °C, at least about 700 °C, at least about 750 °C, at least about 800 °C, at least about 850 °C, at least about 900 °C, at least about 950 °C, at least about 1000 °C, at least about 1 100 °C, at least about 1500 °C, at least about 2000 °C, and at least about 2500 °C. Preferred ranges include between about 750 about and 3000 °C, between about 850 and 2500 °C, between about 950 and about 2500 °C, between about 950 and about 1500 °C, between about 750 about and 3100 °C, between about 850 and 2500 °C, or between about 950 and about 2500 °C.

The time of heating can range from less than a second to many minutes. For example, the time of heating can be less than about 0.5 seconds, less than about 1 second, less than about 5 seconds, less than about 10 seconds, less than about 20 seconds, less than about 30 seconds, or less than about 1 min. The time of heating can be at least about 1 minute, at least about 2 minutes, at least about 5 minutes, at least about 15 minutes, at least about 30 minutes, at least about 45 minutes, at least about 60 minutes, at least about 90 minutes, at least about 120 minutes, at least about 150 minutes, at least about 240 minutes, from about 0.01 seconds to about 240 minutes, from about 0.5 seconds to about 240 minutes, from about 1 second to about 240 minutes, from about 1 minute to about 240 minutes, from about 0.01 seconds to about 60 minutes, from about 0.5 seconds to about 60 minutes, from about 1 second to about 60 minutes, from about 1 minute to about 60 minutes, from about 0.01 seconds to about 10 minutes, from about 0.5 seconds to about 10 minutes, from about 1 second to about 10 minutes, from about 1 minute to about 10 minutes, from about 0.01 seconds to about 1 minute, from about 0.5 seconds to about 1 minute, from about 1 second to about 1 minute, no more than about 600 minutes, no more than about 450 minutes, no more than about 300 minutes, no more than about 180 minutes, no more than about 120 minutes, no more than about 90 minutes, no more than about 60 minutes, no more than about 30 minutes, no more than about 15 minutes, no more than about 10 minutes, no more than about 5 minutes, no more than about 1 minute, no more than about 30 seconds, no more than about 10 seconds, or no more than about 1 second. During the course of heating, the temperature can vary.

Examples of the rate of heating include at least about 120 °C/min, at least about 200 °C/min, at least about 300 °C/min, at least about 400 °C/min, at least about 600 °C/min, at least about 800 °C/min, at least about 1000 °C/min, at least about 1200

°C/min, at least about 1500 °C/min, at least about 1800 °C/min, and at least about 2000 °C/min.

Graphene sheets can be annealed or reduced to graphene sheets having higher carbon to oxygen ratios by heating under reducing atmospheric conditions (e.g., in systems purged with inert gases or hydrogen). Reduction/annealing temperatures are preferably at least about 300 °C, or at least about 350 °C, or at least about 400 °C, or at least about 500 °C, or at least about 600 °C, or at least about 750 °C, or at least about 850 °C, or at least about 950 °C, or at least about 1000 °C. The temperature used can be, for example, between about 750 about and 3000 °C, or between about 850 and 2500 °C, or between about 950 and about 2500 °C.

The time of heating can be for example, at least about 1 second, or at least about 10 second, or at least about 1 minute, or at least about 2 minutes, or at least about 5 minutes. In some embodiments, the heating time will be at least about 15 minutes, or about 30 minutes, or about 45 minutes, or about 60 minutes, or about 90 minutes, or about 120 minutes, or about 150 minutes. During the course of annealing/reduction, the temperature can vary within these ranges.

The heating can be done under a variety of conditions, including in an inert atmosphere (such as argon or nitrogen) or a reducing atmosphere, such as hydrogen (including hydrogen diluted in an inert gas such as argon or nitrogen), or under vacuum. The heating can be done in any appropriate vessel, such as a fused silica or a mineral or ceramic vessel or a metal vessel. The materials being heated including any starting materials and any products or intermediates) can be contained in an essentially constant location in single batch reaction vessel, or can be transported through one or more vessels during the reaction in a continuous or batch reaction. Heating can be done using any suitable means, including the use of furnaces and infrared heaters.

The graphene sheets preferably have a surface area of at least about 100 m²/g to, or of at least about 200 m²/g, or of at least about 300 m²/g, or of least about 350 m²/g, or of least about 400 m²/g, or of least about 500 m²/g, or of least about 600 m²/g., or of least about 700 m²/g, or of least about 800 m²/g, or of least about 900 m²/g, or of least about 700 m²/g. The surface area can be about 400 to about 1 100 m²/g. The theoretical maximum surface area can be calculated to be 2630 m²/g. The surface area includes all values and subvalues therebetween, especially including 400, 500, 600, 700, 800, 900, 1000, 1 100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, and 2630 m²/g.

The graphene sheets can have number average aspect ratios of about 100 to about 100,000, or of about 100 to about 50,000, or of about 100 to about 25,000, or of about 100 to about 10,000 (where "aspect ratio" is defined as the ratio of the longest dimension of the sheet to the shortest). Surface area can be measured using either the nitrogen adsorption/BET method at 77 K or a methylene blue (MB) dye method in liquid solution.

The dye method is carried out as follows: A known amount of graphene sheets is added to a flask. At least 1.5 g of MB are then added to the flask per gram of graphene sheets. Ethanol is added to the flask and the mixture is ultrasonicated for about fifteen minutes. The ethanol is then evaporated and a known quantity of water is added to the flask to re-dissolve the free MB. The undissolved material is allowed to settle, preferably by centrifuging the sample. The concentration of MB in solution is determined using a UV-vis spectrophotometer by measuring the absorption at _max = 298 nm relative to that of standard concentrations.

The difference between the amount of MB that was initially added and the amount present in solution as determined by UV-vis spectrophotometry is assumed to be the amount of MB that has been adsorbed onto the surface of the graphene sheets. The surface area of the graphene sheets are then calculated using a value of 2.54 m² of surface covered per one mg of MB adsorbed.

The graphene sheets can have a bulk density of from about 0.01 to at least about 200 kg/m³. The bulk density includes all values and subvalues therebetween, especially including 0.05, 0.1 , 0.5, 1 , 5, 10, 15, 20, 25, 30, 35, 50, 75, 100, 125, 150, and 175 kg/m³.

The graphene sheets can be functionalized with, for example, oxygen-containing functional groups (including, for example, hydroxyl, carboxyl, and epoxy groups) and typically have an overall carbon to oxygen molar ratio (C/O ratio), as determined by bulk elemental analysis, of at least about 1 :1 , or more preferably, at least about 3:2.

Examples of carbon to oxygen ratios include about 3:2 to about 85:15; about 3:2 to about 20:1 ; about 3:2 to about 30:1 ; about 3:2 to about 40:1 ; about 3:2 to about 60:1 ; about 3:2 to about 80:1 ; about 3:2 to about 100:1 ; about 3:2 to about 200:1 ; about 3:2 to about 500:1 ; about 3:2 to about 1000:1 ; about 3:2 to greater than 1000:1 ; about 10:1 to about 30:1 ; about 80:1 to about 100:1 ; about 20:1 to about 100:1 ; about 20:1 to about 500:1 ; about 20:1 to about 1000:1 ; about 50:1 to about 300:1 ; about 50:1 to about 500:1 ; and about 50:1 to about 1000:1. In some embodiments, the carbon to oxygen ratio is at least about 10:1 , or at least about 15:1 , or at least about 20:1 , or at least about 35:1 , or at least about 50: 1 , or at least about 75: 1 , or at least about 100: 1 , or at least about 200:1 , or at least about 300:1 , or at least about 400:1 , or at least 500:1 , or at least about 750:1 , or at least about 1000:1 ; or at least about 1500:1 , or at least about 2000:1 . The carbon to oxygen ratio also includes all values and subvalues between these ranges.

The graphene sheets can contain atomic scale kinks. These kinks can be caused by the presence of lattice defects in, or by chemical functionalization of the two- dimensional hexagonal lattice structure of the graphite basal plane.

The compositions can further comprise graphite (including natural, Kish, and synthetic, annealed, pyrolytic, highly oriented pyrolytic, etc. graphites). The ratio by weight of graphite to graphene sheets can be from about 2:98 to about 98:2, or from about 5:95 to about 95:5, or from about 10:90 to about 90:10, or from about 20:80 to about 80:20, or from about 30:70 to 70:30, or from about 40:60 to about 90:10, or from about 50:50 to about 85:15, or from about 60:40 to about 85:15, or from about 70:30 to about 85:15.

The graphene sheets can comprise two or more graphene powders having different particle size distributions and/or morphologies. The graphite can also comprise two or more graphite powders having different particle size distributions and/or morphologies.

The graphene sheets or graphene sheets and graphite, if present, can be present in the composition in about 0.01 to about 30 weight percent, or about 0.1 to about 30 weight percent, or about 0.5 to about 30 weight percent, or about 1 to about 30 weight percent, or about 2 to about 30 weight percent, or about 3 to about 30 weight percent, or about 4 to about 30 weight percent, or about 5 to about 30 weight percent, or about 6 to about 30 weight percent, or about 0.01 to about 20 weight percent, or about 0.1 to about 20 weight percent, or about 0.5 to about 20 weight percent, or about 1 to about 20 weight percent, or about 2 to about 20 weight percent, or about 3 to about 20 weight percent, or about 4 to about 20 weight percent, or about 5 to about 20 weight percent, or about 6 to about 20 weight percent, or about 0.01 to about 15 weight percent, or about 0.1 to about 15 weight percent, or about 0.5 to about 15 weight percent, or about 1 to about 15 weight percent, or about 2 to about 15 weight percent, or about 3 to about 15 weight percent, or about 4 to about 15 weight percent, or about 5 to about 15 weight percent, or about 6 to about 15 weight percent, or about 0.01 to about 10 weight percent, or about 0.1 to about 10 weight percent, or about 0.5 to about 10 weight percent, or about 1 to about 10 weight percent, or about 2 to about 10 weight percent, or about 3 to about 10 weight percent, or about 4 to about 10 weight percent, or about 5 to about 10 weight percent, or about 6 to about 10 weight percent, or about 0.01 to about 8 weight percent, or about 0.1 to about 8 weight percent, or about 0.5 to about 8 weight percent, or about 1 to about 8 weight percent, or about 2 to about 8 weight percent, or about 3 to about 8 weight percent, or about 4 to about 8 weight percent, or about 5 to about 8 weight percent, or about 6 to about 8 weight percent, or about 0.01 to about 6 weight percent, or about 0.1 to about 6 weight percent, or about 0.5 to about 6 weight percent, or about 1 to about 6 weight percent, or about 2 to about 6 weight percent, or about 3 to about 6 weight percent, or about 4 to about 6 weight percent, or about 5 to about 6 weight percent, or about 0.01 to about 4 weight percent, or about 0.1 to about 4 weight percent, or about 0.5 to about 4 weight percent, or about 1 to about 4 weight percent, or about 2 to about 4 weight percent, or about 3 to about 4 weight percent, or about 0.01 to about 3 weight percent, or about 0.1 to about 3 weight percent, or about 0.5 to about 3 weight percent, or about 1 to about 3 weight percent, or about 2 to about 3 weight percent, or about 0.01 to about 2 weight percent, or about 0.1 to about 2 weight percent, or about 0.5 to about 2 weight percent, or about 1 to about 2 weight percent, or about 0.01 to about 1 weight percent, or about 0.1 to about 1 weight percent, or about 0.5 to about 1 weight percent, based on the total weight of the graphene sheets (or graphene sheets and graphite, if present) and the polymer(s).

The graphene sheets (and/or graphite, if present) can be combined with one or more solvents in the form of a paste, dispersion, suspension that can be combined with the polymer when the composition or article is formed. Some of all of the solvent can be removed from the composition or article during or after processing.

The graphene sheet (and/or graphite, if present)-solvent combination can be made using any suitable method, such as milling, grinding blending, dispersing, etc. by using suitable mixing, dispersing, and/or compounding techniques and apparatus, including ultrasonic devices, high-shear mixers, ball mills, attrition equipment, sandmills, two-roll mills, three-roll mills, cryogenic grinding crushers, extruders, kneaders, double planetary mixers, triple planetary mixers, high pressure homogenizers, horizontal and vertical wet grinding mills, etc.) Processing technologies can be wet or dry and can be continuous or discontinuous. Suitable materials for use as grinding media include metals, carbon steel, stainless steel, ceramics, stabilized ceramic media (such as cerium yttrium stabilized zirconium oxide), PTFE, glass, tungsten carbide, etc. Methods such as these can be used to change the particle size and/or morphology of the graphene sheets (and/or graphite, if present). Examples of solvents include water, distilled or synthetic isoparaffinic

hydrocarbons (such Isopar® and Norpar® (both manufactured by Exxon) and Dowanol® (manufactured by Dow), citrus terpenes and mixtures containing citrus terpenes (such as Purogen, Electron, and Positron (all manufactured by Ecolink)), terpenes and terpene alcohols (including terpineols, including alpha-terpineol), limonene, aliphatic petroleum distillates, alcohols (such as methanol, ethanol, n-propanol, /^'-propanol, n-butanol, /^'- butanol, sec-butanol, ie f-butanol, pentanols, i-amyl alcohol, hexanols, heptanols, octanols, diacetone alcohol, butyl glycol, etc.), ketones (such as acetone, methyl ethyl ketone, cyclohexanone, /^'-butyl ketone, 2,6,8,trimethyl-4-nonanone etc.), esters (such as methyl acetate, ethyl acetate, n-propyl acetate, /-propyl acetate, n-butyl acetate, /^'-butyl acetate, fe/t-butyl acetate, carbitol acetate, etc.), glycol ethers, ester and alcohols (such as 2-(2-ethoxyethoxy)ethanol, propylene glycol monomethyl ether and other propylene glycol ethers; ethylene glycol monobutyl ether, 2-methoxyethyl ether (diglyme), propylene glycol methyl ether (PGME); and other ethylene glycol ethers; ethylene and propylene glycol ether acetates, diethylene glycol monoethyl ether acetate, 1 -methoxy-2- propanol acetate (PGMEA); and hexylene glycol (such as Hexasol™ (supplied by SpecialChem)), dibasic esters (such as dimethyl succinate, dimethyl glutarate, dimethyl adipate), dimethylsulfoxide (DMSO), 1 ,3-dimethyl-3,4,5,6-tetrahydro-2(1 H)-pyrimidinone (DMPU), imides, amides (such as dimethylformamide (DMF), dimethylacetamide, etc.), cyclic amides (such as /V-methylpyrrolidone and 2-pyrrolidone), lactones (such as beta- propiolactone, gamma-valerolactone, delta-valerolactone, gamma-butyrolactone, epsilon-caprolactone), cyclic imides (such as imidazolidinones such as Ν,Ν'- dimethylimidazolidinone (1 ,3-dimethyl-2-imidazolidinone)), and mixtures of two or more of the foregoing and mixtures of one or more of the foregoing with other carriers.

Solvents can be low- or non-VOC solvents, non-hazardous air pollution solvents, and non-halogenated solvents.

The articles are useful in many environments where they will be used at elevated temperatures. The articles can be used to replace metal components in many applications (including hoses, seals, gaskets, etc.).

The articles can be used in environments where they are exposed to hot air and other gases, steams, hot water and other fluids, fuels, lubricants, coolants, hot materials, etc.

Examples of articles include seals, gaskets, o-rings, bushing, cables, cable coatings and jackets, seats, mounts (such as motor or engine mounts), pipes, tubes, hoses, panels, panels, body panels, wire coatings and jackets, belts, tires, couplings, couplings, connectors, joints, insulators, flex joints, valves and valve components, power transfer belts, material handling belts, housings, etc.

The articles can be components of pumps, such as vacuum pumps, diaphragm pumps, impeller pumps, piston pumps, positive displacement pumps, etc. They can be components of or serve as pump heads, vanes, float balls, piping, tubing, hoses, seals, connectors, valves, belts, apparel, etc.

The articles can be components of water heaters, chemical reactors and production systems, mixers and mills, steam lines and steam handling systems, power plants, furnaces, ovens, kilns, boilers, dryers, furnaces, stoves, food processing equipment, mining and smelting equipment, heating and cooling systems, heat dissipation systems, generators, hot air conveyer systems, conveying systems, etc

The articles can be used as engine and motor components, such as gaskets, belts, tubes and hoses, engine or motor mounts, etc.

The articles can be used in fuel transmission lines, natural gas transmission lines, etc.

The articles can be used in batteries and other energy capture and storage devices, such as high temperature flow batteries (such as in flow loops and salt baths), solar energy systems (e.g. photovoltaic and thermal collection systems (such as heaters)), geothermal power systems, wind power systems, nuclear power systems, etc.

The articles can be used in industrial and manufacturing applications such as furnaces, mills, steel mills, smelters, foundries, cement furnaces, autoclaves, ovens, metallurgy, casting, refining, ceramics, polymers (such as plastics, etc.), glass, minerals, power plants, chemical processing, reactors, food processing, mining, farming, materials transfer systems, piping systems, steam production, safety systems and components, engine rooms (including engine rooms exposed to high steam and other high

temperature sources), glass and mineral processing, suction cups for handling hot glass, etc.

The articles can be used in electrical systems, such as transformer components, wire and power line coating, sheathing, cladding, jacketing etc., wiring for use in plenum spaces, insulators, etc.

The articles can be used in applications where fire retardancy and/or drip suppression are important. The articles can be used as components in weapons systems such as firearms (including small firearms, artillery, etc.), projectile launch tubes (such as torpedo launch tubes). They can be used in explosives and pyrotechnics (including fireworks) systems, etc.

The articles can be used in apparel and personal protective equipment for high temperature uses, when exposure to high temperatures is possible, etc. such as that used by industrial workers, welders, construction works, chemical plant workers, foundry workers, emergency personnel (such as firefighters, first responders, rescue workers, hazmat workers, etc.), military personnel, electrical workers, etc. Example include, but are not limited to boots, shoes, and other footwear, gaiters, overboots, spats, chaps, coats, jackets, pants, belts, shirts, undergarments, hoods, visors, glasses, goggles, chin guards, gloves, mittens, smocks, aprons, bibs, overalls, coveralls, hats, hard hats, helmets, respirators, gas masks, blankets, fire curtains, breathing air (such as tanks, such as oxygen tanks) equipment (such as tubing, face masks, etc.), harnesses and lanyards, space suits, etc.

The articles can be used as components of conveyer systems, such as belts, rollers, drive rollers, etc. These include conveyer systems that transport materials, ore and finished metal products, food products, etc. They include conveyer systems that transport items to and from ovens, furnaces, kilns, boilers, dryers, and other high temperature sources. Examples of conveyer systems include those used in metal processing and smelting, chemical processing, fuel (e.g. coal, etc.) transport and feeding, assembly and production lines (such as those used to make automobiles and other vehicles), casting (such as metal casting), packaging, waste handling and recycling, etc.

Where metal roller and other components can be replaced, the articles can offer an increased coefficient of friction that can reduce belt wear.

The articles can be used as comments of high temperature printing systems (e.g. laser printing, digital printing, flexographic printing, gravure printing, etc., such as fusers, belts, gears, etc.

The articles can be used in aerospace, aviation, space exploration, etc.

applications. Examples include aircraft, airplanes, helicopters, rockets, satellites, booster engines, re-entry vehicles, balloons (including weather balloons, weather balloons), airships, blimps, dirigibles, drones, space shuttles, space stations,

interplanetary and intergalactic exploration devices and vehicles, etc. The articles can be used in automotive applications, such as engine mounts, belts, timing belts, drive belts, transmission belts, seals, gaskets, boots (e.g. constant velocity boots), body panels, heaters, tubing, coolant system components, etc.

The articles can be used for cooking and baking (e.g., heat resistant cookware and bakeware) and laboratory equipment.

In some cases the composite compositions can be electrically and/or thermally conductive. In some embodiments, the articles can have a conductivity of at least about 10^"8 S/m. It can have a conductivity of about 10^"6 S/m to about 10⁵ S/m, or of about 10^"5 S/m to about 10⁵ S/m. In other embodiments of the invention, the coating has conductivities of at least about 0.001 S/m, of at least about 0.01 S/m, of at least about 0.1 S/m, of at least about 1 S/m, of at least about 10 S/m, of at least about 100 S/m, or at least about 1000 S/m, or at least about 10,000 S/m, or at least about 20,000 S/m, or at least about 30,000 S/m, or at least about 40,000 S/m, or at least about 50,000 S/m, or at least about 60,000 S/m, or at least about 75,000 S/m, or at least about 10⁵ S/m, or at least about 10⁶ S/m.

In some cases, the surface resistivity of the composite composition can be no greater than about 10 megaQ/square/mil, or no greater than about 1 mega Ω/square/mil, or no greater than about 500 kiloQ/square/mil, or no greater than about 200

kiloQ/square/mil, or no greater than about 100 kiloQ/square/mil, or no greater than about 50kiloQ/square/mil, or no greater than about 25 kiloQ/square/mil, or no greater than about 10 kiloQ/square/mil, or no greater than about 5 kilo Ω/square/mil, or no greater than about 1000 Ω/square/mil, or no greater than about 700 Ω/square/mil, or no greater than about 500 Ω/square/mil, or no greater than about 350 Ω/square/mil, or no greater than about 200 Ω/square/mil, or no greater than about 200 Ω/square/mil, or no greater than about 150 Ω/square/mil, or no greater than about 100 Ω/square/mil, or no greater than about 75 Ω/square/mil, or no greater than about 50 Ω/square/mil, or no greater than about 30 Ω/square/mil, or no greater than about 20 Ω/square/mil, or no greater than about 10 Ω/square/mil, or no greater than about 5 Ω/square/mil, or no greater than about 1 Ω/square/mil, or no greater than about 0.1 Ω/square/mil, or no greater than about 0.01 Ω/square/mil, or no greater than about 0.001 Ω/square/mil.

In some cases, the composite composition can have a thermal conductivity of about 0.1 to about 50 W/nvK, or of about 0.5 to about 30 W/nvK, or of about 0.1 to about 0.5 W/nvK, or of about 0.1 to about 1 W/nvK, or of about 0.1 to about 5 W/nvK, or of about 0.5 to about 2 W/nvK, or of about 1 to about 5 W/nvK, or of about 0.1 to about 0.5 W/rrvK, or of about 0.1 to about 50 W/nvK, or of about 1 to about 30 W/rrvK, or of about 1 to about 20 W/rrvK, or of about 1 to about 10 W/rrvK, or of about 1 to about 5 W/rrvK, or of about 2 to about 25 W/rrvK, or of about 5 to about 25 W/rrvK, or of at least about 0.7 W/rrvK, or of at least 1 W/rrvK, or of at least 1.5 W/rrvK, or of at least 3 W/rrvK, or of at least 5 W/rrvK, or of at least 7 W/rrvK, or of at least 10 W/rrvK, or of at least 15 W/m^«K.

Claims

A method of using an article, comprising heating the article to a temperature of at least about 100 °C, wherein the article comprises a composition comprising at least one polymer and graphene sheets.

The method of claim 1 , wherein the article is heated to a temperature of at least about 150 °C.

The method of claim 1 , wherein the article is heated to a temperature of at least about 200 °C.

The method of claim 1 , wherein the polymer comprises at least one rubber or elastomer.

The method of claim 1 , wherein the graphene sheets have a surface area of at least about 300 m²/g.

The method of claim 1 , wherein the composition further comprises graphite.

The method of claim 1 , wherein the composition comprises from about 0.1 to about 10 weight percent graphene sheets, based on the total weight of graphene sheets and polymer.

A method of using an article, wherein the article comprises a first composition comprising at least one polymer, graphene sheets, and, optionally, additional components, comprising heating the article to a temperature above which a second composition that is identical to the first composition except that it has no graphene sheets has a storage modulus that is at least about 10 percent less than the storage modulus of the second composition at 25 °C.

The method of claim 8, wherein the article is heated to a temperature of at least about 150 °C.

10. The method of claim 8, wherein the polymer comprises at least one rubber or elastomer.

1 1. The method of claim 8, wherein the graphene sheets have a surface area of at least about 300 m²/g.

12. The method of claim 8, wherein the composition further comprises graphite.

13. The method of claim 8, wherein the composition comprises from about 0.1 to about 10 weight percent graphene sheets, based on the total weight of graphene sheets and polymer.

14. A method of using an article, wherein the article comprises a first composition comprising at least one polymer, graphene sheets, and, optionally, additional components, comprising heating the article to a temperature that is at about or greater than the heat deflection temperature of a second composition that is identical to the first composition except that it has no graphene sheets.

15. The method of claim 14, wherein the article is heated to a temperature of at least about 200 °C.

16. The method of claim 14, wherein the polymer comprises at least one rubber or elastomer.

17. The method of claim 14, wherein the graphene sheets have a surface area of at least about 300 m²/g.

18. The method of claim 14, wherein the composition further comprises graphite.

19. The method of claim 14, wherein the composition comprises from about 0.1 to about 10 weight percent graphene sheets, based on the total weight of graphene sheets and polymer.