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Polytetrafluoroethylene compositesRelated Patent Categories: Stock Material Or Miscellaneous Articles, Composite (nonstructural Laminate)Polytetrafluoroethylene composites description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070036980, Polytetrafluoroethylene composites. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a divisional of U.S. patent application Ser. No. 10/814,885 filed on Mar. 31, 2004, the disclosure of which is incorporated herein by reference. INTRODUCTION [0002] This invention relates to composites comprising polytetrafluoroethylene. In particular, the present invention relates to a composition for bonding polytetrafluoroethylene articles into composites, to methods for preparing a surface of a polytetrafluoroethylene article for use with a bonding composition, and to composites formed by use of bonding composition as coating upon the prepared surface of a polytetrafluoroethylene article. [0003] Polytetrafluoroethylene materials are well known for their remarkably low adhesion to many items such as food, metal, and fluid materials. Polytetrafluoroethylene materials also provide benefits in chemically resistant surfaces and components. Teflon.TM. polytetrafluoroethylene (Dupont Corporation) and Halon.TM. polytetrafluoroethylene (Allied Chemical Corporation) are two well-established commercial/industrial product families in this regard. [0004] While polytetrafluoroethylene is not fragile, its use must take into account a modest robustness in environments where mechanical stress is asserted against an article made from it. In this regard, polytetrafluoroethylene is frequently bonded to a structural material (such as steel) in items such as cookware. In many sealing applications, a polytetrafluoroethylene component is protectively mechanically pressed or held into a desired position without adhesive attachment to a structural material. [0005] The innate challenge in bonding polytetrafluoroethylene to a structural material is the very property of polytetrafluoroethylene that makes it so useful--it doesn't "stick" to many materials. In one attempt to solve this problem, metals are adhered to polytetrafluoroethylene by chemically etching a surface of the polytetrafluoroethylene article and bonding the chemically etched surface of the polytetrafluoroethylene to the metal through use of a coupling agent (such as a silane coupling agent). However, there remains a need for effective methods for adhering metallic and non-metallic structural articles to polytetrafluoroethylene. These and other needs are achieved with the present invention. SUMMARY [0006] The invention provides a composite, comprising: [0007] (a) a polytetrafluoroethylene portion having an etched surface; and [0008] (b) a structural material portion (made of polymer, metal, ceramic, leather, or wood) bonded to the etched surface at an interface, the interface comprising a cured admixture of from about 10 to about 90 weight percent tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer, from about 0.01 to about 1 weight percent polyethylene-oxide-modified silicone polymer coupling agent, and an oxygen-radical-containing copolymer (an epoxy polymer, phenoxy polymer, or hydroxylated diamine-diepoxide derivative copolymer), and having less than about 5, preferably less than about 1, weight percent water [0009] In a further aspect, the invention provides an aqueous admixture of: [0010] (a) from about 10 to about 90 weight percent fluoropolymer aqueous emulsion having from about 20 to about 60 weight percent tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride emulsified terpolymer, a pH from about 6 to about 10, a specific gravity from about 1.1 to about 1.5 grams per milliliter, and a viscosity from about 4 to about 12 Mega Pascal Seconds; and [0011] (b) oxygen-radical-containing copolymer aqueous solution in remainder, the oxygen-radical-containing copolymer aqueous solution having [0012] (1) from about 20 to about 60 weight percent of the oxygen-radical-containing copolymer with a softening temperature of from about 25 to about 180 degrees Centigrade, a specific gravity from about 1.1 to about 1.5 grams per milliliter, and an estimated equivalent molecular weight from about 100 to about 10,000, and [0013] (2) from about 0.01 to about 1 weight percent polyethylene-oxide-modified silcone polymer coupling agent having a wax melting temperature of from about 25 to about 50 degrees Centigrade. [0014] In yet a further aspect of the invention, a method of making a composite is provided by: [0015] (a) admixing an aqueous admixture of from about 10 to about 90 weight percent of the above-described fluoropolymer aqueous emulsion with a remainder of the above-described oxygen-radical-containing copolymer aqueous solution; [0016] (b) etching a surface of a polytetrafluoroethylene article to provide an etched surface; [0017] (c) saturatively distributing the aqueous admixture onto the etched surface; [0018] (d) positioning a structural material article (polymer, metal, ceramic, leather, or wood) against the aqueous admixture on the etched surface so that the aqueous admixture fluidly fills an interface between the structural material article and the etched surface; and [0019] (e) curing the aqueous admixture in the interface to bond the structural material article to the etched surface. [0020] In yet a further aspect of the invention, a method for etching an article made of polytetrafluoroethylene, is provided though: [0021] (a) generating a bombardment beam (using a plasma beam, an electron-beam, or a laser beam); and [0022] (b) etching a surface of the article with the bombardment beam, the bombardment beam energizing the surface with sufficient energy for dislodging a plurality of fluoride atoms from the polytetrafluoroethylene of the surface and thereby generating residual fluoroethylenic free radical moieties in polytetrafluoroethylene polymeric chains of the surface upon conclusion of the etching. [0023] In various embodiments, the structural material is any of a polyester thermoplastic elastomer, polyamide thermoplastic elastomer, thermoplastic urethane elastomer, fluoroelastomer, ethylene acrylic rubber thermoplastic vulcanizate, acrylic acid ester rubber/polyacrylate rubber thermoplastic vulcanizate, silicone-thermoplastic vulcanizate, polyether-block co-polyamide polymer, ethylene-propylene-diamine monomer rubber/polypropylene thermoplastic vulcanizate, polyamide, polyester, polyolefin, polyphenylene-sulfide, polyether-ether ketone, polyamide-imide, polysulfone, thermoplastic urethane, acrylonitrile-butadiene-styrene, polyvinyl chloride, polymethylmethacrylate, polycarbonate, polybutene, cellulosic plastic, polyacrylate, a polyacetal, or a combination of these. [0024] In one embodiment, an inert particulate is admixed in one of the above polymeric materials. This inert particulate is any of calcium carbonate, carbon black, graphite, silica fume, kaolin, magnetizable ferrite powder, metal fiber, carbon nanotubes, carbon fiber, glass fiber, fiberglass fiber, microspheres, polyimide powder, molybdenum sulfide powder, brass powder, or a combination of these materials. [0025] In one embodiment, the structural material is a metal such as steel, carbon steel, stainless steel, or aluminum. [0026] In one embodiment, the polytetrafluoroethylene surface is prepared by sodium-ammonia solution etching or sodium-naphthalene solution etching. [0027] In one embodiment, the structural material portion is bonded to the etched surface by use any of calendaring, pultrusion, multilayer extrusion, or co-injection molding. [0028] In one embodiment, a composite according to the above (or made by the above) is a seal, a gasket, an o-ring, a hose for chemical and/or fuel handling, or a diaphragm in a diaphragm pump. [0029] Further areas of applicability will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. DESCRIPTION [0030] The following definitions and non-limiting guidelines must be considered in reviewing the description of this invention set forth herein. [0031] The headings (such as "Introduction" and "Summary") and sub-headings (such as "Amplification") used herein are intended only for general organization of topics within the disclosure of the invention, and are not intended to limit the disclosure of the invention or any aspect thereof. In particular, subject matter disclosed in the "Introduction" may include aspects of technology within the scope of the invention, and may not constitute a recitation of prior art. Subject matter disclosed in the "Summary" is not an exhaustive or complete disclosure of the entire scope of the invention or any embodiments thereof. [0032] The citation of references herein does not constitute an admission that those references are prior art or have any relevance to the patentability of the invention disclosed herein. All references cited in the Description section of this specification are hereby incorporated by reference in their entirety. [0033] The description and specific examples, while indicating embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. Moreover, recitation of multiple embodiments having stated features is not intended to exclude other embodiments having additional features, or other embodiments incorporating different combinations the stated of features. Continue reading about Polytetrafluoroethylene composites... 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