Shell Chemical Co.Houston, Tx.

Gear wear in the toner-cartridge assembly of a laser printer can give the machine the jitters, resulting in poor print quality. So when Lexmark International Inc., Lexington, Ky., heard of the low wear and quiet operation of gears based on new Carilon thermoplastic polymers, it began evaluations that resulted in a switch from a higher-priced lubricated acetal gear in its high-end Optra network laser printer. Excellent wear resistance in power-transfer applications like gears and bearings is but one of a wide range of performance properties of this new set of aliphatic polyketone engineering polymers introduced by Shell in October. "What Carilon thermoplastic polymers offer is not a single unique characteristic, but a combination of properties not found in any existing class of engineering thermoplastic polymers," says Ellen McGowan, business manager for Carilon polymers. "Their exceptional value lies in their broad range of performance characteristics, such that customers do not have to sacrifice one property to gain another. We believe this is one of the most significant developments in the engineering-thermoplastic-polymers industry since the introduction of nylon and polycarbonate." While development was still underway in 1994, polyketone polymers were recognized by the National Assn. for Science, Technology & Society as one of the 12 most significant advances in materials research in the last decade. Finally introduced after more than 20 years in the laboratory, Carilon aliphatic polyketones are semicrystalline polymers with high melting points (in the range of 225 C), exhibiting a range of valuable physical, mechanical, and chemical perform-ance characteristics that are maintained at high temperatures. In addition to high abrasion resistance, strength, stiffness, and toughness, they resist swelling and chemical attack from a range of organic solvents, fuels, and aggressive aqueous media. This chemical resistance is combined with excellent barrier properties to minimize permeation of hydrocarbon vapors and oxygen, making them excellent candidates for piping and fuel-handling applications under-hood or underground. "In the automotive industry, investigations are already underway for Carilon polymers in fuel lines and connectors, fuel-pump components, fuel tanks, filters, injection rails, inlet manifolds, gears, wheel covers, and exterior parts," says McGowan. Carilon polymers have high fatigue and creep resistance and withstand repetitive deformation, making them eminently suitable for snap-fit assemblies in appliance applications, for instance. Flame resistance (accomplished without the addition of toxic halogen or phosphorous-containing flame retardants) combined with stiffness, impact resistance, and elongation hold promise for electrical and electronic applications from current-carrying and non-current-carrying devices to electro- magnetic parts. Low moisture absorption also translates to no predrying prior to molding or extrusion, which is accomplished under conventional fabrication conditions. Film, fiber, and protective coatings are also potential applications for Carilon engineering thermoplastic polymers, which will be available as neat resin and compounded into glass-reinforced, flame-retard-ant, and tribological grades.