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  Composite material of continuous fiber and ultra high molecular weight polyethyleneRelated Patent Categories: Fabric (woven, Knitted, Or Nonwoven Textile Or Cloth, Etc.), Coated Or Impregnated Woven, Knit, Or Nonwoven Fabric Which Is Not (a) Associated With Another Preformed Layer Or Fiber Layer Or, (b) With Respect To Woven And Knit, Characterized, Respectively, By A Particular Or Differential Weave Or Knit, Wherein The Coating Or Impregnation Is Neither A Foamed Material Nor A Free Metal Or Alloy LayerThe Patent Description & Claims data below is from USPTO Patent Application 20050287891. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority under 35 U.S.C. .sctn. 119 from provisional application Ser. No. 60/578,420, filed Jun. 9, 2004, and entitled "A Composite Material of Continuous Fiber and Ultra High Molecular Weight Polyethylene". FIELD OF THE INVENTION [0002] This invention relates generally to the art of composite materials, more particularly to composite materials comprising thermoplastics and high strength fibers. BACKGROUND OF THE INVENTION [0003] Thermoplastics are plastics that are made by heating resin pellets or powders (the raw material) until they melt, molding the material to a desired shape, and then resolidifying the material through a cooling process. Because the chemistry of the plastic does not change, this process can be performed multiple times. In other words, thermoplastics can be reprocessed or recycled with additional heating and cooling. Additionally, the manufacturing process for thermoplastic products can be as quick as the heating, molding, and cooling processes can occur (e.g. seconds). Hence thermoplastics have the manufacturing advantages of rapid processing and multi-step manufacturing, both of which can translate and have translated to significant benefits and cost savings. [0004] Some common thermoplastics are polyethylene "PE", polypropylene "PP", polyamide "PA" (more commonly known as nylon) and polyethylene terepthalate "PET" (more commonly known as polyester). Products made from such thermoplastics are very diverse, for example, toys, rope, clothing and bottles. Melt temperatures for most thermoplastics fall between 125.degree. C. and 300.degree. C. In their softened or partially melted state thermoplastics flow under pressure and thus can be shaped by processes such as injection molding, blow molding and extrusion. [0005] Thermoplastics have many excellent qualities. Metals, however, generally have much higher strength and stiffness than thermoplastics. To increase the strength and/or stiffness of thermoplastics it has long been known that mixing thermoplastic resins with short high strength fibers results in a product with substantially increased strength and/or stiffness. Often higher temperature properties are also improved. This mixing is done either before melting the thermoplastic resin or as the thermoplastic resin is melted but in either case before forming the product by extrusion or injection molding, as disclosed for example in U.S. Pat. No. 3,577,378. Types of fiber commonly used for this purpose may be glass, carbon, aramid or other materials which have suitably high strength and/or stiffness and melt temperatures above the thermoplastic of choice. [0006] These materials are sometimes referred to as short fiber composites or more commonly fiber reinforced plastics "FRP". Such FRP materials typically comprise 10 to 30 percent fiber by weight with the balance being the thermoplastic of choice. The fibers are typically 0.1 to 5 mm in length. The use of higher percentages of fiber and/or longer fibers is typically avoided because of difficulties achieving good flow of the mixture and good uniform dispersion and distribution of the fibers, unacceptable accumulation of the fibers in the nozzle of the injection molding equipment, and unacceptable reduction in toughness and impact strength in the product. [0007] Typically with the short fibers from 0.1 to 5 mm in length, FRP thermoplastics have tensile and/or flexural strength and stiffness up to 5 times greater than the same thermoplastic without the reinforcing fibers. [0008] U.S. Pat. No. 3,577,378 teaches that the added tensile and flexural strength and stiffness is due to the high strength and stiffness of the fibers coupled with the excellent mixing and distribution of the fibers in the polymer and the ease with which the molten FRP material flows in the extruder and injection mold. There is possibly, however, a characteristic loss of impact strength in the short fiber FRP product compared with the unreinforced thermoplastic product as reported with respect to polycarbonate in U.S. Pat. No. 3,577,378. [0009] A more current example of the enhanced strength and stiffness properties of FRP comes from Victrex plc, headquartered at Hillhouse International in Lancashire, UK. Victrex is the world's largest producer of certain high performance high temperature engineered thermoplastics, in particular polyetheretherketone (PEEK). Published Victrex data for unreinforced "150G" PEEK and 30% short carbon fiber reinforced "150CA30" PEEK is indicative of the difference in properties that successful introduction of short fibers can produce, as illustrated in FIG. 1. This data is excerpted from Victrex USA Inc. publication 1100/2.5m titled PEEK Material Properties Guide. Both materials are suitable for extrusion and injection molding. [0010] Engineers and designers, however, continue to seek materials which have strength and stiffness that exceed conventional FRP short fiber thermoplastics and that also have strength to weight and stiffness to weight ratios that are higher than those of metals. In the past twenty five years several processes have been invented wherein thermoplastic composites have been produced with continuous fibers and with fiber content as high as 70%. These materials generally have much higher strength and/or stiffness than short fiber FRP materials. In fact these composites exhibit strength and/or stiffness comparable and in many cases superior to metals, including steel. Also, generally, the density of these materials is much lower than metals. Hence their strength to weight and stiffness to weight ratios are much higher than metals, including steel. U.S. Pat. No. 4,680,224 discloses a preferred method for producing such continuous fiber thermoplastic composites. [0011] This APC-2 thermoplastic composite manufactured by Cytec Engineering Materials, a division of Cytec, Inc. It is made with continuous unidirectional AS4 carbon fiber and PEEK thermoplastic resin. For illustration of the enhanced strength of these continuous fiber composite thermoplastics, FIG. 2 depicts selected mechanical properties at room temperature of APC-2. The fiber content in this composite is 68% by weight. Note the enhanced properties in the fiber direction as compared to the unreinforced PEEK and the FRP short fiber PEEK properties listed in FIG. 2. The strength in the fiber direction is 9 times greater than the 150CA30 short fiber PEEK FRP and more than 20 time greater than the unreinforced 150 PEEK. The strength and stiffness perpendicular to the fibers is however, much lower. The tensile strength perpendicular to the fibers is approximately the same as the unreinforced resin while the stiffness perpendicular to the fibers is about double the unreinforced resin. [0012] These values clearly demonstrate both the tremendous strength and stiffness of continuous fiber thermoplastic composites and the influence of fiber direction at the same time. This directional or non-isotropic nature of continuous fiber composites allows the designer much greater freedom to create optimized designs when compared to most conventional plastics and metals which have more or less isotropic or non directional properties. If the designer is desirous of more isotropic properties in the thermoplastic composite, any number of layers of this material having fibers in various directions may be combined under heat and pressure to create a more isotropic material. Most often multiples of 4 layers are used with -45.degree., 0.degree., 45.degree., 90.degree. fiber orientations to produce what are termed "quasi-isotropic" material properties. [0013] Advanced Materials engineers finally discovered how to manufacture more complex thermoplastic composites with difficult plastics. The initial process consisted of adding chemical solvents to the heated thermoplastic resin, to make the resin sufficient watery to saturate a mass of fibers. Although this solvent had to be removed later in the process, composite manufacturers could now produce a thermoplastic composite with a relatively even distribution of plastic matrix to hold the fibers in place. [0014] Such methods of producing short fiber reinforced thermoplastics as described above are widely practiced today with virtually all thermoplastics, but not with UHMW PE. However, is UHMW PE has a linear polyethylene structure just like high density polyethylene but its molecules are exceptionally large, having a molecular weight of from 2 to 6 million daltons. This high molecular weight provides UHMW PE with exceptional impact strength and abrasion resistance; however, it also results in special well known processing characteristics which preclude use of standard extrusion and molding techniques. In short, UHMW PE does not "flow" at high temperature as do virtually all other thermoplastics. In fact, when attempting to injection mold UHMW PE, the extreme pressures result in shear-degradation of the polymer. [0015] Because of UHMW PE's unusual behavior, the processes used to make UHMW PE stock materials (plate, sheet and bar being the most common forms of UHMW PE) are most akin to compression molding or sintering. The typical procedure is to fill a form or mold with UHMW PE in powder form and then apply heat and pressure to remove the air between the particles and to force the particles to soften and deform and fuse into a single mass. This ideally results in an essentially void free solid although microscopic porosity will still exist. In some special cases a lower pressure is used specifically to produce a porous structure. This porous solid form of UHMW PE is sometimes used for filtration. These processes do not require the UHMW PE to flow. [0016] Desiring reinforced products of UHMW PE, many individuals have sought ways to successfully add short fibers to UHMW PE. U.S. Pat. Nos. 4,055,862, 5,622,767 and 5,620,770 disclose successful methods for making such "FRP" materials with UHMW PE and carbon fibers without requiring the UHMW PE or the fibers to flow wherein the carbon fibers may be up to 8 mm long. These patents disclose methods that are essentially the same as the method described above for making unreinforced UHMW PE materials. In these "compression molding like" or "sintering like" methods the short carbon fibers are mechanically mixed with the particles of UHMW PE powder prior to introducing the mixture to the form or mold, and prior to melting the UHMW PE. SUMMARY OF THE INVENTION [0017] In one embodiment of the invention, the invention relates to composite material of continuous fibers and ultra high molecular weight polyethylene, the composite material comprising ultra high molecular weight polyethylene, and continuous high strength fibers, wherein the ultra high molecular weight polyethylene forms a continuous matrix among and surrounding the fibers. [0018] In another embodiment of the invention, the invention relates to a composite material of continuous fibers and ultra high molecular weight polyethylene, the composite material comprising ultra high molecular weight polyethylene; continuous high strength fibers, wherein the ultra high molecular weight polyethylene forms a continuous matrix among and surrounding the fibers; and at least one additive or filler. [0019] The invention also relates to a method of manufacturing an ultra high molecular weight polyethylene composite, the method comprising selecting unidirectional and continuous high strength fibers; impregnating the fibers with ultra high molecular weight polyethylene in a fine powder to form a composite; optionally adding additives or fibers to the composite; and forming a continuous matrix of the ultra high molecular weight polyethylene surrounding the fibers. [0020] The techniques described above, however, until the present invention, did not particularly work well with UHMW plastics. It is an object of the invention to provide a composite material of continuous fiber and ultra high molecular weight polyethylene (UHMW PE) exhibits many improved physical properties in comparison to both unreinforced and short fiber reinforced UHMW PE. Another object of the invention is to improve strength and stiffness in the fiber direction as well as thermal and electrical conductivity when a highly conductive fiber is employed. It is yet another object of the invention to provide a composite that exhibits many of the outstanding characteristics of unreinforced UHMW PE, such as excellent abrasion resistance, low coefficient of friction and high PV. Continue reading... Full patent description for Composite material of continuous fiber and ultra high molecular weight polyethylene Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Composite material of continuous fiber and ultra high molecular weight polyethylene patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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