Novel Material and Process for Replacement of Lead Products

Lead is a soft, low melting point, high density, and inexpensive material that can be shaped easily. All of these attributes have made lead useful in applications such as bullets, fishing rod sinkers, weights for balancing tires, hunting shots, etc. In spite of these attractive properties, lead is a major environmental contaminant because of its toxicity. Lead can be stored in biological tissues with devastating results. Extensive use of lead in common applications has resulted in this material appearing in the food chain (through its deposition on soil, waters, and plants). One high-volume application of lead is in the automotive sector, in which lead is used as balancing weights (0.25 ounces to 3 ounces). When these weights fall off of vehicle wheels, they add pure lead to the ground, which is extremely toxic. Because the lead is easy to melt and form, many of these weights are converted into weights for fishing line sinkers. Game hunting using lead shots has become another major source of environmental contamination in which the unused lead is deposited on the surface soil as well as sometimes in water. It is, therefore, of utmost importance that an environmentally benign substitute for lead that can be formed into complex shapes be established quickly. Ideally, if the substitute material can be recycled and if a part of it can degrade in an environmentally benign manner, it would provide a tremendous advantage. The goal of Materials Processing, Inc.'s research project is to develop a conceptual composite material from a special spherical high-density inorganic particulate material (benign relative to lead) that is highly loaded in a special organic thermoplastic material. This special mix will have the density of lead-based alloys (around 11 g/cc), will be injection-moldable into complex shapes, have the ability to be recycled, and in special cases can partially degrade in a benign manner. Phase I success will provide a material and process capable of replacing lead-based alloys in numerous applications, including tire-balancing weights, shots used in hunting, bullets for test ranges, radiation shields, fishing line sinkers, etc. It is expected that lead will suffer the same fate as "asbestos," and its use gradually will be phased out from numerous applications before 2010. This project will provide U.S. industries with an alternative material that has numerous attributes and is "manufacturing friendly."