New options in natural-fiber reinforced composites. (Keeping Up with Composites).Two new developments in natural-fiber reinforced polypropylene polypropylene (pŏl'ēprō`pəlēn), plastic noted for its light weight, being less dense than water; it is a polymer of propylene. It resists moisture, oils, and solvents. composites could expand their range of applications in automotive parts. Improved wood fibers Rayonier in Jesup, Ga., has developed a high-purity cellulose cellulose, chief constituent of the cell walls of plants. Chemically, it is a carbohydrate that is a high molecular weight polysaccharide. Raw cotton is composed of 91% pure cellulose; other important natural sources are flax, hemp, jute, straw, and wood. fiber derived from local hard and soft woods. What makes the 1- to 2.2-mm-long, 20- to 40-micron-diam. TerraCel wood fibers different is their high (95% or above) content of pure alpha-cellulose. Generally, wood contains less than 50% alpha-cellulose together with lignin lignin (lĭg`nĭn), a highly polymerized and complex chemical compound especially common in woody plants. The cellulose walls of the wood become impregnated with lignin, a process called lignification, which greatly increases the strength and and other components that impair the fibers' physical and thermal properties. John Underwood This article is about the early 17th century actor. For the U.S. Representative from Georgia, see John W. H. Underwood. John Underwood (d. October 1624) was an early 17th century actor, a member of the King's Men, the company of William Shakespeare. , Rayonier's market-development manager, says a 30%-reinforced PP composite using these wood fibers can achieve stiffiness exceeding that of mineral-filled PP and approaching short-glass reinforced compounds. In Europe, TerraCel composites are in advanced testing by independent compounders for automotive OEMs. The fibers have a density of 1.25 to 1.5 g/cc, which typically is more than 50% lighter than glass or mineral reinforcements. In addition, the fibers are non-abrasive, resistant to breakage in numerous reuse cycles, and free of residual ash when incinerated. Equally important, the high cellulose level in Rayonier fibers boosts their ability to resist degradation up to around 527 F. Conventional wood flours Wood flour is finely pulverized wood that has a consistencey fairly equal to sand, but can vary considerably, with particles ranging in size from a fine powder to roughly the size of a grain of rice. and fibers typically withstand no more than 392 F. Consequently, conventional wood reinforcement has been largely restricted to PP matrix materials. Rayonier's wood fiber is being used at 30% levels in nylon 6, which has a melting point melting point, temperature at which a substance changes its state from solid to liquid. Under standard atmospheric pressure different pure crystalline solids will each melt at a different specific temperature; thus melting point is a characteristic of a substance and of around 437 F. A modified screw design keeps peak temperatures below the fibers' degradation point. "Nylon 6 broadens the potential of fiber-reinforced compounds in more severe end-uses," Underwood claims. He says compounders are also developing 30% wood/mineral-filled nylon 6 hybrid compounds as potential replacements for mineral- and short-glass reinforced compounds in under-the-hood and semi-structural applications. Tel: (912) 427-5000, www.rayonier.com Mold decorative panels Meanwhile, Cannon Tecnos in Milan, Italy, has manufactured a complete production system (photo) for compression molding Compression molding is a method of molding in which the molding material, generally preheated, is first placed in an open, heated mold cavity. The mold is closed with a top force or plug member, pressure is applied to force the material into contact with all mold areas, and heat decorative auto-interior parts using a flax-reinforced PP sheet. Tecnos proposes this material as an alternative to conventional GMT (Greenwich Mean Time) See UTC. GMT - Universal Time 1 sheet. Initial commercial use is a six-piece trunk liner molded in a single shot for Audi in Germany. Carlos Ortenzi, Tecnos' market manager, says the sheet is a sandwich of a PP core and flax-reinforced PP skins. Tecnos' system introduces the preheated flax/PP sheet into the press simultaneously with two outer layers of a printable print·a·ble adj. 1. Capable of being printed or of producing a print: printable negatives. 2. Fit for publication: printable language. polyester non-woven rollstock that is cold-fed into the system without contacting the PP sheet prior to molding. The double-acting press has movable upper and lower platens to improve the balance of flow in the mold. Tecnos supplies the press, preheating oven, automatic sheet-feeding and centering equipment, unwinding stations, and automatic roll-change systems for the decorative rollstock. The line produces six parts a minute. Tel: +39 331 406811, www.cannon.com |
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