Thermoplastic composite gets the lead out

Cleveland, OH -Weigh the costs and benefits of using lead, and the scales don't always tip in favor of this toxic material, creating a big opportunity for alternatives. One such lead-replacement candidate was announced last month by M.A. Hanna Engineered Materials (Norcross, GA), which has weighed in with a high-density thermoplastic for weighting, balancing, and radiation-shielding applications.

Called ECOMASS, these new composites can offer a specific gravity equal to that of lead alloy without any of the toxicity, according to Thomas Wilkinson, the company's VP of commercial compounds. The compounds consist of a non-toxic tungsten filler in a variety of base resins-including, so far, olefins and nylon copolymers. At up to 80% filler, "the plastic acts mostly as a binder," Wilkinson notes.

Eight ECOMASS formulations are currently available, covering a specific gravity range from 6.0 to 11.0 and offering a variety of mechanical property combinations.

Among them is an ECOMASS compound intended for radiation-shielding applications, in nuclear medicine, medical imaging, and radiation therapy. With a specific gravity of 6.9, its density comes in at roughly 35% that of lead. At the same time, it provides what the company reports as more than 90% lead shielding equivalency at typical X-ray energy levels.

Other grades have already turned up in non-toxic projectile inserts for small caliber ammunition. And still other grades are targeted at weight-and-balance applications in industrial machinery, sporting goods, and instrumentation markets. With mass properties so similar to lead, Wilkinson says, ECOMASS can serve as a "drop-in" replacement for the toxic material in applications that don't depend on lead's chemical properties-such as batteries. "But it's a drop-in with better yield strength," he adds. Suitable for injection molding, the composites can also be painted or plated in conventional finishing processes, Wilkinson adds.

For more information on ECOMASS from M.A. Hanna: Circle 539