Patent Application
20150140319
1. Field of Use
This disclosure is generally directed to surface layers for fuser members useful in electrophotographic imaging apparatuses, including digital, image on image, and the like.
2. Background
Thermal conductivity is an important property for coatings used for thermal control. Fuser topcoats with high thermal conductivity enable higher fusing speed, wider fusing latitude, and lower fusing temperature. Therefore, various thermally conductive fillers have been disclosed for this purpose. Graphene is a unique filler material which possesses combination of superior mechanical strength and conductivity. However, it is challenging to utilize graphene material to reinforce and improve thermal conductivity in polymer composites, as graphene particles agglomerate and are therefore difficult to uniformly disperse into a polymer composite. Poorly dispersed graphene particles in polymer composites cause defects which lead to polymer composites having reduced mechanical strength and poor thermal conductivity.
Fuser surfaces having increased thermal conductivity without negatively impacting fusing performance are desired.
According to an embodiment, there is provided a fuser member including a substrate and a release layer disposed on the substrate. The release layer includes non-woven polymer fibers having graphene particles dispersed along the fibers. The release layer includes a fluoropolymer dispersed throughout the non-woven polymer fibers.
According to another embodiment, there is provided a method of manufacturing a fuser member. The method includes providing a conductive surface. Polymeric fibers are electrospun on the conductive surface to form a non-woven polymer fiber layer. A dispersion of graphene particles and a first solvent is flow coated on the non-woven polymer fiber layer. The first solvent is removed to form a non-woven polymer fiber layer having graphene particles deposited along the polymer fibers. A mixture of a fluoropolymer and a second solvent is coated on the non-woven polymer fiber layer having graphene particles deposited along the polymer fibers having deposited graphene particles. The mixture is heated to remove the second solvent and to melt or cure the fluoropolymer thereby forming a release layer.
According to an embodiment, there is provided a fuser member including a substrate, an intermediate layer disposed on the substrate and a release layer. The release layer is disposed on the substrate. The release layer includes non-woven polymer fibers having graphene particles dispersed along the fibers. The release layer includes a fluoropolymer dispersed throughout the non-woven polymer fibers.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the present teachings and together with the description, serve to explain the principles of the present teachings.
It should be noted that some details of the FIGS. have been simplified and are drawn to facilitate understanding of the embodiments rather than to maintain strict structural accuracy, detail, and scale.
Reference will now be made in detail to embodiments of the present teachings, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
In the following description, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific exemplary embodiments in which the present teachings may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present teachings and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present teachings. The following description is, therefore, merely exemplary.
Illustrations with respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” The term “at least one of” is used to mean one or more of the listed items can be selected.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of embodiments are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein. For example, a range of “less than 10” can include any and all sub-ranges between (and including) the minimum value of zero and the maximum value of 10, that is, any and all sub-ranges having a minimum value of equal to or greater than zero and a maximum value of equal to or less than 10, e.g., 1 to 5. In certain cases, the numerical values as stated for the parameter can take on negative values. In this case, the example value of range stated as “less than 10” can assume negative values, e.g. −1, −2, −3, −10, −20, −30, etc.
Disclosed herein is a composition including electrospun fibers. Graphene particles are deposited along the electrospun fibers. A polymer matrix is dispersed throughout the electrospun fibers having the deposited graphene particles. The graphene particles are uniformly distributed along the fibers. The polymer matrix is a low surface energy polymeric material which fills the gaps between the electrospun fibers. The electrospun fiber materials selected are high performance polymers. The fiber network provides a framework for the graphene particles. The graphene particles are uniformly distributed along the electrospun fibers. This produces a thermally conductive layer at low loadings of the graphene particles. In addition, the electrospun fibers enable uniform distribution of graphene particles or nanoparticles in the coating layer without the need for reformulation of the graphene dispersion with a fluoropolymer. A fluoropolymer matrix material is used to provide low surface energy of the layer, which is essential for non-stick application such as for fusers.
In various embodiments, the fixing member can include, for example, a substrate, with one or more functional layers formed thereon. The substrate can be formed in various shapes, e.g., a cylinder (e.g., a cylinder tube), a cylindrical drum, a belt, or a film, using suitable materials that are non-conductive or conductive depending on a specific configuration, for example, as shown in
Specifically,
In
The belt substrate 210 (
Examples of intermediate or functional layers 120 (
Examples of intermediate or functional layers 120 (
The fluoroelastomers VITON GH® and VITON GF® have relatively low amounts of vinylidenefluoride. The VITON GF® and VITON GH® have about 35 weight percent of vinylidenefluoride, about 34 weight percent of hexafluoropropylene, and about 29 weight percent of tetrafluoroethylene, with about 2 weight percent cure site monomer. Cure site monomers are available from Dupont.
For a roller configuration, the thickness of the intermediate or functional layer can be from about 0.5 mm to about 10 mm, or from about 1 mm to about 8 mm, or from about 2 mm to about 7 mm. For a belt configuration, the functional layer can be from about 25 microns up to about 2 mm, or from 40 microns to about 1.5 mm, or from 50 microns to about 1 mm.
The release layer or surface layer includes electrospun fibers. Graphene particles are deposited along the electrospun fibers. A polymer matrix is dispersed throughout the electrospun fibers having the deposited graphene particles. The graphene particles are uniformly distributed along the fibers. The polymer matrix is a low surface energy polymeric material which fills the gaps between the electrospun fibers.
Optionally, any known and available suitable adhesive layer may be positioned between the outer layer or surface layer and the intermediate layer or between the intermediate layer and the substrate layer. Examples of suitable adhesives include silanes such as amino silanes (such as, for example, HV Primer 10 from Dow Corning), titanates, zirconates, aluminates, and the like, and mixtures thereof. In an embodiment, an adhesive in from about 0.001 percent to about 10 percent solution can be wiped on the substrate. The adhesive layer can be coated on the substrate, or on the outer layer, to a thickness of from about 2 nanometers to about 10,000 nanometers, or from about 2 nanometers to about 1,000 nanometers, or from about 2 nanometers to about 5000 nanometers. The adhesive can be coated by any suitable known technique, including spray coating or wiping.
The release layer is manufactured by providing a substrate layer that is conductive. The substrate layer, described previously, can include one or more intermediate layers. Polymeric fibers are electrospun on the conductive surface to form a non-woven polymer fiber layer. Intermediate layers can be interposed between the substrate and the electrospun fibers. A dispersion including graphene particles and a solvent is flow coated on the electrospun polymeric fibers. The solvent is removed to form graphene particles uniformly deposited along the electrospun polymer fibers. A mixture of a fluoropolymer in a solvent is flow coated on the polymer fibers having the deposited graphene particles. The mixture is to remove the second solvent and melt or cure the fluoropolymer thereby having the fluoropolymer penetrate the electrospun fibers having the deposited graphene particles to form the release layer.
Nonwoven fabrics are broadly defined as sheet or web structures bonded together by entangling fiber or filaments (and by perforating films) mechanically, thermally or chemically. They include flat, porous sheets that are made directly from separate fibers or from molten plastic or plastic film. They are not made by weaving or knitting and do not require converting the fibers to yarn.
The fuser release layer is fabricated by applying the polymer fibers onto a substrate by an electrospinning process. Electrospinning uses an electrical charge to draw very fine (typically on the micro or nano scale) fibers from a liquid. The charge is provided by a voltage source. The process does not require the use of coagulation chemistry or high temperatures to produce solid threads from solution. This makes the process particularly suited to the production of fibers using large and complex molecules such as polymers. When a sufficiently high voltage is applied to a liquid droplet, the body of the liquid becomes charged, and electrostatic repulsion counteracts the surface tension and the droplet is stretched. At a critical point a stream of liquid erupts from the surface. This point of eruption is known as the Taylor cone. If the molecular cohesion of the liquid is sufficiently high, stream breakup does not occur and a charged liquid jet is formed.
Electrospinning provides a simple and versatile method for generating ultrathin fibers from a rich variety of materials that include polymers, composites and ceramics. To date, numerous polymers with a range of functionalities have been electrospun as nanofibers. In electrospinning, a solid fiber is generated as the electrified jet (composed of a highly viscous polymer solution with a viscosity range of from about 1 to about 400 centipoises, or from about 5 to about 300 centipoises, or from about 10 to about 250 centipoises) is continuously stretched due to the electrostatic repulsions between the surface charges and the evaporation of solvent. Suitable solvents include dimethylformamide, dimethylacetamide, 1-methyl-2-pyrrolidone, tetrahydrofuran, a ketone such as acetone, methylethylketone, dichloromethane, an alcohol such as ethanol, isopropyl alcohol, water and mixtures thereof. The weight percent of the polymer in the solution ranges from about 1 percent to about 60 percent, or from about 5 percent to about 55 percent to from about 10 percent to about 50 percent.
Exemplary materials used for the electrospun fiber with or without a fluoropolymer sheath can include: polyamide such as aliphatic and/or aromatic polyamide, polyester, polyimide, fluorinated polyimide, polycarbonate, polyurethane, polyether, polyoxadazole, polybenzimidazole, polyacrylonitrile, polycaprolactone, polyethylene, polypropylenes, acrylonitrile butadiene styrene (ABS), polybutadiene, polystyrene, polymethyl-methacrylate (PMMA), poly(vinyl alcohol), poly(ethylene oxide), polylactide, poly(caprolactone), poly(ether imide), poly(ether urethane), poly(arylene ether), poly(arylene ether ketone), poly(ester urethane), poly(p-phenylene terephthalate), cellulose acetate, poly(vinyl acetate), poly(acrylic acid), polyacrylamide, polyvinylpyrrolidone, hydroxypropylcellulose, poly(vinyl butyral), poly(alkly acrylate), poly(alkyl methacrylate), polyhydroxybutyrate, fluoropolymer, poly(vinylidene fluoride), poly(vinylidene fluoride-co-hexafluoropropylene), fluorinated ethylene-propylene copolymer, poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether), poly((perfluoroalkyl)ethyl methacrylate), cellulose, chitosan, gelatin, protein, and mixtures thereof. In embodiments, the electrospun fibers can be formed of a tough polymer such as Nylon, polyimide, and/or other tough polymers.
Exemplary materials used for the electrospun fibers when there is no sheath or coating include fluoropolymers selected from the group consisting of: copolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoropropylene and tetrafluoroethylene; terpolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene; tetrapolymers of vinylidenefluoride, hexafluoropropylene, tetrafluoroethylene, and a cure site monomer; polytetrafluoroethylene (PTFE); perfluoroalkoxy polymer resin (PFA); copolymers of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP); copolymers of hexafluoropropylene (HFP) and vinylidene fluoride (VDF or VF2); terpolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VDF), and hexafluoropropylene (HFP); and tetrapolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VF2), and hexafluoropropylene (HFP) and a cure site monomer.
In embodiments, fluorinated polyimides (FPI) are used for the core with or without a sheath of the polymers in the non-woven matrix layer. Fluorinated polyimides are synthesized in high molecular weight using a known procedure as shown in Equation 1.
wherein one of Ar1 and Ar2 independently represent an aromatic group of from about 4 carbon atoms to about 60 carbon atoms; and at least one of Ar1 and Ar2 further contains fluorine. In the polyimide above, n is from about 30 to about 1000, or from about 40 to about 450 or from about 50 to about 400.
More specific examples of fluorinated polyimides include the following general formula:
wherein Ar1 and Ar2 independently represent an aromatic group of from about 4 carbon atoms to about 100 carbon atoms, or from about 5 to about 60 carbon atoms, or from about 6 to about 30 carbon atoms such as such as phenyl, naphthyl, perylenyl, thiophenyl, oxazolyl; and at least one of Ar1 and Ar2 further contains a fluoro-pendant group. In the polyimide above, n is from about 30 to about 500, or from about 40 to about 450 or from about 50 to about 400.
Ar1 and Ar2 can represent a fluoroalkyl having from about 4 carbon atoms to about 100 carbon atoms, or from about 5 carbon atoms to about 60 carbon atoms, or from about 6 to about 30 carbon atoms.
In embodiments, the electrospun fibers can have a diameter ranging from about 5 nm to about 50 μm, or ranging from about 50 nm to about 20 μm, or ranging from about 100 nm to about 1 μm. In embodiments, the electrospun fibers can have an aspect ratio of about 100 or higher, e.g., ranging from about 100 to about 1,000, or ranging from about 100 to about 10,000, or ranging from about 100 to about 100,000. In embodiments, the non-woven fabrics can be non-woven nano-fabrics formed by electrospun nanofibers having at least one dimension, e.g., a width or diameter, of less than about 1000 nm, for example, ranging from about 5 nm to about 500 nm, or from 10 nm to about 100 nm.
In embodiments, the sheath on the polymer fibers is formed by coating the polymer fiber core with a fluoropolymer and heating the fluoropolymer. The fluoropolymers have a curing or melting temperature of from about 150° C. to about 360° C. or from about 280° C. to about 330° C. The thickness of the sheath can be from about 10 nm to about 200 microns, or from about 50 nm to about 100 microns or from about 200 nm to about 50 microns.
In an embodiment core-sheath polymer fiber can be prepared by co-axial electrospinning of polymer core and the fluoropolymer (such as Viton) to form the non-woven core-sheath polymer fiber layer.
Examples of fluoropolymers useful as the sheath or coating of the polymer fiber include fluoroelastomers. Fluoroelastomers are from the class of 1) copolymers of two of vinylidenefluoride, hexafluoropropylene, and tetrafluoroethylene; 2) terpolymers of vinylidenefluoride, hexafluoropropylene, and tetrafluoroethylene; and 3) tetrapolymers of vinylidenefluoride, hexafluoropropylene, tetrafluoroethylene, and a cure site monomer. These fluoroelastomers are known commercially under various designations such as VITON A®, VITON B® VITON E® VITON E 60C®, VITON E430®, VITON 910®, VITON GH®; VITON GF®; and VITON ETP®. The VITON® designation is a trademark of E.I. DuPont de Nemours, Inc. The cure site monomer can be 4-bromoperfluorobutene-1,1,1-dihydro-4-bromoperfluorobutene-1,3-bromoperfluoropropene-1,1,1-dihydro-3-bromoperfluoropropene-1, or any other suitable, known cure site monomer, such as those commercially available from DuPont. Other commercially available fluoropolymers include FLUOREL 2170®, FLUOREL 2174®, FLUOREL 2176®, FLUOREL 2177® and FLUOREL LVS 76®, FLUOREL® being a registered trademark of 3M Company. Additional commercially available materials include AFLAS™ a poly(propylene-tetrafluoroethylene), and FLUOREL II® (LII900) a poly(propylene-tetrafluoroethylenevinylidenefluoride), both also available from 3M Company, as well as the Tecnoflons identified as FOR-60KIR, FOR-LHF®, NM® FOR-THF®, FOR-TFS®, TH®, NH®, P757®, TNS®, T439®, PL958®, BR9151® and TN505, available from Solvay Solexis.
Examples of three known fluoroelastomers are (1) a class of copolymers of two of vinylidenefluoride, hexafluoropropylene, and tetrafluoroethylene, such as those known commercially as VITON A®; (2) a class of terpolymers of vinylidenefluoride, hexafluoropropylene, and tetrafluoroethylene known commercially as VITON B®; and (3) a class of tetrapolymers of vinylidenefluoride, hexafluoropropylene, tetrafluoroethylene, and cure site monomer known commercially as VITON GH® or VITON GF®.
The fluoroelastomers VITON GH® and VITON GF® have relatively low amounts of vinylidenefluoride. The VITON GF® and VITON GH® have about 35 weight percent of vinylidenefluoride, about 34 weight percent of hexafluoropropylene, and about 29 weight percent of tetrafluoroethylene, with about 2 weight percent cure site monomer.
Examples of fluoropolymers useful as the sheath or coating on the polymer fiber core include fluoroplastics. Fluoroplastics suitable for use herein include fluoropolymers comprising a monomeric repeat unit that is selected from the group consisting of vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene, perfluoroalkylvinylether, and mixtures thereof. Examples of fluoroplastics include polytetrafluoroethylene (PTFE); perfluoroalkoxy polymer resin (PFA); copolymer of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP); copolymers of hexafluoropropylene (HFP) and vinylidene fluoride (VDF or VF2); terpolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VDF), and hexafluoropropylene (HFP); and tetrapolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VF2), and hexafluoropropylene (HFP), and mixtures thereof.
In embodiments, the electrospun fibers can have a diameter ranging from about 5 nm to about 50 μm, or ranging from about 50 nm to about 20 μm, or ranging from about 100 nm to about 1 μm. In embodiments, the electrospun fibers can have an aspect ratio about 100 or higher, e.g., ranging from about 100 to about 1,000, or ranging from about 100 to about 10,000, or ranging from about 100 to about 100,000. In embodiments, the non-woven fabrics can be non-woven nano-fabrics formed by electrospun nanofibers having at least one dimension, e.g., a width or diameter, of less than about 1000 nm, for example, ranging from about 5 nm to about 500 nm, or from 10 nm to about 100 nm.
After providing the non-woven fibers on the substrate, the graphene particles are deposited along the fibers in a uniform manner by coating a graphene particle dispersion and removing the solvent.
Any suitable type of graphene particles can be employed in the dispersion of the present disclosure. In an embodiment, the graphene particles can include graphene, graphene platelets and mixtures thereof. Graphene particles have a width of from about 0.5 microns to about 10 microns. In embodiments the width can be from about 1 micron to about 8 microns, or from about 2 microns to about 5 microns. Graphene particles have a thickness of from about 1 nanometer to about 50 nanometers. In embodiments the thickness can be from about 2 nanometers to about 8 nanometers, or from about 3 nanometers to about 6 nanometers. In an embodiment, graphene particles can have a relatively large per unit surface area, such as, for example, about 120 to 150 m2/g. Such graphene-comprising particles are well known in the art.
The graphene particles are dispersed in a solvent including water, and any organic solvents, toluene, hexane, cyclohexane, heptane, tetrahydrofuran, ketones, such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, N-Methylpyrrolidone (NMP); amides, such as dimethylformamide (DMF); N,N′-dimethylacetamide (DMAc), sulfoxides, such as dimethyl sulfoxide; alcohols, ethers, esters, hydrocarbons, chlorinated hydrocarbons, and mixtures of any of the above. The solid content of the dispersion of graphene particles is from about 0.1 weight percent to about 10 weight percent, or in embodiments from about 0.5 weight percent to about 5 weight percent of from about 1 weight percent to about 3 weight percent.
The graphene dispersion may further comprise a stabilizer selected from the group consisting of non-ionic surfactants, ionic surfactants, polyacids, polyamines, polyelectrolytes, and conductive polymers. More specifically the stabilizer includes polyacrylic acid, copolymer of polyacrylic acid, polyallylamine, polyethylenimine, polydiallyldimethylammonium chloride), poly(allylamine hydrochloride), poly(3,4-ehtylenedioxythiophene), poly(3,4-ethylenedioxythiophene) complexes with a polymer acid, Nafion (a sulfonated tetrafluoroethylene), gum arabic, and or chitosan. The amount of stabilizer in the graphene dispersion formulation ranges from about 0.1 percent to about 200 percent by weight of graphene particles, or from about 0.5 percent to about 100 percent by weight of graphene particles, or from about 1 percent to about 50 percent by weight of graphene particles.
A fluoropolymer coating is provided throughout the electrospun fibers having deposited graphene particles. The fluoropolymer coating composition can include, an effective solvent, in order to disperse the fluoropolymer that are known to one of ordinary skill in the art.
The fluoropolymer coating can include a fluoroelastomer which have been listed previously. Fluoroelastomers include copolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoropropylene and tetrafluoroethylene, terpolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene, tetrapolymers of vinylidenefluoride, hexafluoropropylene, tetrafluoroethylene, and a cure site monomer.
The fluoropolymer coating can include a fluoroplastic. Fluoroplastics includes polytetrafluoroethylene (PTFE); perfluoroalkoxy polymer resin (PFA); copolymers of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP); copolymers of hexafluoropropylene (HFP) and vinylidene fluoride (VDF or VF2); terpolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VDF), and hexafluoropropylene (HFP); and tetrapolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VF2), and hexafluoropropylene (HFP) and a cure site monomer; and mixtures thereof.
The fluoropolymer coating can include a cross-linked perfluoropolyether is available from Shin-Etsu (Tradename SIFEL®).
where n is a number of from about 0 to about 5000.
Therefore, the term “coating” or “coating technique” is not particularly limited in the present teachings, and dip coating, painting, brush coating, roller coating, pad application, spray coating, spin coating, casting, or flow coating can be employed.
The fluoropolymer coating is cured or melted at a temperature of from about 255° C. to about 360° C. or from about 280° C. to about 330° C.
Fluoropolymers suitable for use as in the release layer having the metal mesh include fluoropolymers listed previously. Fluoroplastics have a melting temperature of from about 280° C. to about 400° C. or from about 290° C. to about 390° C. or from about 300° C. to about 380° C. while fluoroelastomers are cured at a temperature of from about 80° C. to about 250° C.
The thermal resistivity the release layer of the electrospun fibers having graphene particles deposited thereon and a fluoropolymer dispersed throughout is from about 102 to about 108 Ω/cm and the thermal conductivity is from about 0.25 W/mK to about 10 W/mK.
The release layer described herein has a thickness of from about 10 μm to about 400 μm, or from about 20 μm to about 300 μm, or from about 25 μm to about 200 μm.
Specific embodiments will now be described in detail. These examples are intended to be illustrative, and not limited to the materials, conditions, or process parameters set forth in these embodiments. All parts are percentages by solid weight unless otherwise indicated.
A solution of about 8 weight percent fluorinated polyimide (FPI) in methyl ethyl ketone was loaded into a 10 mL syringe. A solution of 8 weight percent fluoroelastomer (Viton) in methyl ethyl ketone with 5 weight percent A0700 was loaded into a second 10 mL syringe. The two syringes were mounted into their respective syringe pumps, and the syringes were connected to the coaxial spinneret with the FPI on the core channel and the Viton on the shell channel. A roller substrate was wiped clean using isopropanol, and placed onto a fixture (with X-stage and rotation) approximately 15 cm away from the spinneret tip. About 20 kv was applied at the spinneret. Fibers with about 1 μm in diameter were generated and coated on the roll. The non-woven electorspun fibers were held at room temperature overnight and then heat-treated with to cure the fibers.
About 0.08 grams of graphene nanoplatelets (available from STREM, 06-0210) were dispersed in the 80 grams isopropanol and deionized water (1:1) containing 2.3 grams of poly(acrylic acid) water solution (35 weight percent). The dispersion was mixed by sonication for 150 minutes using a 60 percent setting for the power output.
The roller coated with electrospun fibers was mounted on a motorized rotation stage. The graphene dispersion was put in a syringe pump and the flow rate was set at 2 ml/min on the flow coating program. The rotational speed was 123 RPM and the coating speed was 2 mm/s. The coating was allowed to dry at room temperature overnight, followed by heating at 250° C. for 30 minutes to remove the solvents.
Crosslinkable perfluoropolyether was coated onto the graphene fabrics by flow-coating process. The coating was heated about 150° C. for 2 hours to result thermally conductive coatings.
The coating was uniform with a low surface energy.
It will be appreciated that variants of the above-disclosed and other features and functions or alternatives thereof may be combined into other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art, which are also encompassed by the following claims.
